Gas cleaning separator

ABSTRACT

The present invention relates to a separator and more specifically, but not exclusively, to a centrifugal separator for the cleaning of a gaseous fluid. A centrifugal separator is provided as comprising a housing defining an inner space, and a rotor assembly for imparting a rotary motion onto a mixture of substances to be separated. The rotor assembly is located in said inner space and is rotatable about an axis relative to the housing. The rotor assembly comprises an inlet for receiving said mixture of substances, an outlet from which said substances are ejected from the rotor assembly during use, and a flow path for providing fluid communication between the inlet and outlet, wherein the outlet is positioned more radially outward from said axis than the inlet.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.13/383,279 filed Jan. 10, 2012, which claims priority to PCT ApplicationNo. PCT/SE2009/050892, filed Jul. 10, 2009, the subject matter of whichapplications is incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates to a separator and more specifically, butnot exclusively, to a centrifugal separator for the cleaning of agaseous fluid.

BACKGROUND

It is well known that a mixture of fluids having different densities maybe separated from one another through use of a centrifugal separator.One specific use of such a separator is in the separation of oil fromgas vented from a crank case forming part of an internal combustionengine.

With regard to this specific use of separators, there can be a tendencyfor the high pressure gasses found in the combustion chambers of aninternal combustion engine to leak past the associated piston rings andinto the crank casing of the engine. This continuous leaking of gas intothe crank case can lead to an undesirable increase of pressure withinthe crank case and, as a consequence, to a need to vent gas from saidcasing. In large commercial vehicles, vented gas is generallyreintroduced into the inlet manifold of the engine. However, the gasvented from the crank casing typically carries a quantity of engine oil(as droplets or a fine mist), which is picked up from the reservoir ofoil held in the crank casing. More specifically, gas flowing between anengine cylinder and the associated piston tends to pick up lubricatingoil located on the cylinder wall. Also, condensing of oil vapour by anengine's cylinder block cooling system generates an oil mist in thecrank case.

In order to allow vented gas to be introduced into the inlet systemwithout also introducing unwanted oil (particularly into a turbochargingsystem wherein the efficiency of the compressor can be adverselyaffected by the presence of oil), it is necessary to clean the ventedgas (i.e. to remove the oil carried by the gas) prior to the gas beingintroduced into the inlet system. This cleaning process may beundertaken by a centrifugal separator, which is mounted on or adjacentthe crank case and which directs cleaned gas to the inlet system anddirects separated oil back to the crank case.

There are a number of problems associated with some prior art ALFDEX™separators. These problems can be considered in three broad categories.

First, the fluid pathways through the separator give rise to pressurelosses which adversely affect the flow capacity of the separator and,consequently, the size of engine with which the separator can be used.

Second, the arrangement of some of these prior art separators is suchthat, under certain conditions, cleaned gas can become contaminatedbefore leaving the separator.

Third, certain manufacturing techniques and construction featuresassociated with these prior art separators can lead to assemblydifficulties and/or reliability problems.

SUMMARY

The present invention resides in a first aspect in a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space, and

at least one blade element located in said space and rotatable about anaxis so as to impart motion on a mixture of substances to be separated;

a leading edge portion of the at least one blade element comprising aguide surface such that, in use, a mixture of substances flowing towardssaid leading edge portion is guided by the guide surface towardsalignment with the blade element.

The separator recited above with respect to the first aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the first aspect of thepresent invention, comprising a plurality of said blade elementssubstantially equi-spaced about the axis.

A separator as recited above in respect of the first aspect of thepresent invention, comprising twelve of said blade elements locatedabout said axis.

A separator as recited above in respect of the first aspect of thepresent invention, wherein said guide surface comprises a curvedportion.

A separator as recited above in respect of the first aspect of thepresent invention, wherein said guide surface can be provided by a guidevane extending from said leading edge portion.

A separator as recited above in respect of the first aspect of thepresent invention, wherein the guide vane of a blade element is arrangedat an angle to said blade element such that, for a given rotary speed ofsaid blade element about said axis and for a given flow velocity of saidmixture, the guide vane is substantially aligned with the flow ofmixture.

A separator as recited above in respect of the first aspect of thepresent invention, wherein the separator further comprises at least oneseparating disc rotatable about said axis and located in said space soas to receive said substances from a blade element.

A separator as recited above in respect of the first aspect of thepresent invention, wherein the separator comprises a plurality ofseparating discs arranged in a stack, rotatable about the same axis, andlocated in said space so as to receive said substances from the bladeelement.

A separator as recited above in respect of the first aspect of thepresent invention, wherein said axis of the at least one separating discis coincident with said axis of the blade element.

A second aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet; and a housing member defining aregion for receiving fluid ejected from the rotor assembly and directingsaid fluid towards a first outlet aperture of the housing;

an inlet to said region comprises at least one lengthwise portion ofgreater depth than other lengthwise portions of said inlet.

Further features of the present invention recited in the second aspectare provided in a separator as recited below:

A separator as recited above in respect of the second aspect of theinvention, wherein said housing member is located adjacent an end memberof the rotor assembly, said region being defined between the end memberand the housing member.

A separator as recited above in respect of the second aspect of theinvention, wherein said inlet to said region is defined by the endmember and a perimeter edge of the housing member.

A separator as recited above in respect of the second aspect of theinvention, wherein said perimeter edge is circular such that thelengthwise portions of said region inlet extend circumferentially alongsaid edge.

A separator as recited above in respect of the second aspect of theinvention, wherein each lengthwise portion of greater depth is providedby a recess in said perimeter edge which provides greater distancebetween said edge and the end member along each lengthwise portion thanbetween said edge and the end member along said other lengthwiseportions.

A separator as recited above in respect of the second aspect of theinvention, wherein the circular perimeter edge of the housing member isconcentric with said axis.

A separator as recited above in respect of the second aspect of theinvention, wherein each lengthwise portion of greater depth has apart-circular shape extending through an arc of between 45° and 110°,and preferably of 80°.

A separator as recited above in respect of the second aspect of theinvention, wherein said other lengthwise portions have a depth betweenone tenth and one half that of said at least one lengthwise portion andpreferably have a depth one third that of said at least one lengthwiseportion.

A separator as recited above in respect of the second aspect of theinvention, wherein said at least one lengthwise portion is located on anopposite side of the housing member to said first outlet aperture of thehousing.

A separator as recited above in respect of the second aspect of theinvention, wherein said at least one lengthwise portion opens into achannel defined by the housing member for directing fluid towards saidfirst outlet aperture of the housing.

A separator as recited above in respect of the second aspect of theinvention, wherein said at least one lengthwise portion is an inlet tosaid channel, said channel comprising elements at said channel inletwhich, in use, are aligned with the direction of fluid flowing into saidchannel inlet.

A separator as recited above in respect of the second aspect of theinvention, wherein said elements are curved at said channel inlet andstraighten progressively in a downstream direction towards said firstoutlet aperture of the housing.

A separator as recited above in respect of the second aspect of theinvention, wherein said elements comprise opposite side walls definingsaid channel.

A separator as recited above in respect of the second aspect of theinvention, wherein the housing member is located adjacent an end memberof the rotor assembly, said region and channel being defined between theend member and the housing member.

A separator as recited above in respect of the second aspect of theinvention, wherein the distance between the housing member and said endmember of the rotor assembly is greater in one portion of said regionthan in other portions thereof, said one portion thereby defining saidchannel in the housing member.

A separator as recited above in respect of the second aspect of theinvention, wherein said channel comprises a tubular portion.

A third aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet; and

a housing member defining a region for receiving fluid ejected from therotor assembly and directing said fluid towards a first outlet apertureof the housing,

said region comprises a channel extending from one portion of aperimeter edge of the housing member, said portion defining an inlet tosaid channel.

The separator recited above with respect to the second aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the third aspect of theinvention, wherein said channel comprises elements at said channel inletwhich, in use, are aligned with the direction of fluid flowing into saidchannel inlet.

A separator as recited above in respect of the third aspect of theinvention, wherein said elements are curved at said channel inlet andstraighten progressively in a downstream direction towards said firstoutlet aperture of the housing.

A separator as recited above in respect of the third aspect of theinvention, wherein said elements comprise opposite side walls definingsaid channel.

A separator as recited above in respect of the third aspect of theinvention, wherein said channel inlet is located on an opposite side ofthe housing member to said first outlet aperture of the housing.

A separator as recited above in respect of the third aspect of theinvention, wherein said perimeter portion defining the channel inlet hasa part-circular shape extending through an arc of between 45° and 110°,and preferably of 80°.

A separator as recited above in respect of the third aspect of theinvention, wherein the housing member is located adjacent an end memberof the rotor assembly, said region and channel being defined between theend member and the housing member.

A separator as recited above in respect of the third aspect of theinvention, wherein the distance between the housing member and said endmember of the rotor assembly is greater in one portion of said regionthan in other portions thereof, said one portion thereby defining saidchannel in the housing member.

A separator as recited above in respect of the third aspect of theinvention, wherein said channel comprises a tubular portion.

A fourth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet; and

a housing member defining a region for receiving fluid ejected from therotor assembly and directing said fluid towards a first outlet apertureof the housing,

said region comprises a channel having elements at an inlet to saidchannel which, in use, are aligned with the direction of fluid flowinginto said channel inlet.

The separator recited above with respect to the fourth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the fourth aspect of theinvention, wherein said channel extends from one portion of a perimeteredge of the housing member, said portion defining the inlet to saidchannel.

A separator as recited above in respect of the fourth aspect of theinvention, wherein said elements are curved at said channel inlet andstraighten progressively in a downstream direction towards said firstoutlet aperture of the housing.

A separator as recited above in respect of the fourth aspect of theinvention, wherein said elements comprise opposite side walls definingsaid channel.

A separator as recited above in respect of the fourth aspect of theinvention, wherein said channel inlet is located on an opposite side ofthe housing member to said first outlet aperture of the housing.

A separator as recited above in respect of the fourth aspect of theinvention, wherein said perimeter portion defining the channel inlet hasa part-circular shape extending through an arc of between 45° and 110°,and preferably of 80°.

A separator as recited above in respect of the fourth aspect of theinvention, wherein the housing member is located adjacent an end memberof the rotor assembly, said region and channel being defined between theend member and the housing member.

A separator as recited above in respect of the fourth aspect of theinvention, wherein the distance between the housing member and said endmember of the rotor assembly is greater in one portion of said regionthan in other portions thereof, said one portion thereby defining saidchannel in the housing member.

A separator as recited above in respect of the fourth aspect of theinvention, wherein said channel comprises a tubular portion.

A fifth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differencedensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet; and

a housing member defining a region for receiving fluid ejected from therotor assembly and directing said fluid to a first outlet aperture ofthe housing;

the housing member is provided with means for segregating an inlet tosaid region from fluid which, in use, re-circulates back towards saidinlet after having flowed past said inlet.

The separator recited above with respect to the fifth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said segregating means comprises a wall.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall extends from a downstream side of saidregion inlet in a downstream direction with respect to said flow offluid having, in use, past said region inlet.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall is spaced from said housing.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall comprises a free end.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said free end is spaced from said housing in an axialdirection by an axial distance of between 2 mm and 200 mm, andpreferably by a distance of 14 mm.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said free end is spaced from said housing in adirection perpendicular to said axial direction by a distance less thansaid axial distance.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall defines a closed loop.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall defines a frusto-conical shape.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said frusto-conical shape has a longitudinal axiscoincident with said axis of rotation.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said frusto-conical shape diverges in a downstreamdirection with respect to said flow of fluid having, in use, past saidregion inlet.

A separator as recited above in respect of the fifth aspect of theinvention, wherein the housing member comprises means for supporting thehousing member relative to the housing, the supporting means beinglocated downstream of the segregating means with respect to said flow offluid having, in use, past said region inlet.

A separator as recited above in respect of the fifth aspect of theinvention, wherein the supporting means is a wall defining a closedloop.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall has a cylindrical shape.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said wall has a longitudinal axis coincident withsaid axis of rotation.

A separator as recited above in respect of the fifth aspect of theinvention, wherein at least one aperture is provided in said wall at ajunction between said wall and the housing.

A separator as recited above in respect of the fifth aspect of theinvention, further comprising a second outlet aperture of the housing,wherein said supporting means is located in a fluid flow path betweenthe second outlet aperture and said segregating means.

A separator as recited above in respect of the fifth aspect of theinvention, wherein the second outlet aperture is arranged concentricallywith said axis of rotation.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said segregating means is positioned in the housingsuch that, in use, fluid flowing past said region inlet flows on oneside of said segregating means and said fluid which re-circulates flowson another side of said segregating means.

A separator as recited above in respect of the fifth aspect of theinvention, wherein an outlet passage extends between the housing memberand the housing for conveying fluid from said region to the exterior ofthe housing through said outlet aperture, the exterior of said outletpassage being spaced from the housing such that fluid is free to flowabout the entire external perimeter of said outlet passage.

A separator as recited above in respect of the fifth aspect of theinvention, wherein said outlet passage is separate to the housing memberand the housing.

A sixth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

an aperture for permitting the flow of a fluid along a flow path betweenthe exterior of said housing and said inner space, and

a shoulder upstanding from the housing and surrounding said aperture;

the shoulder comprises a curved surface extending inwardly into theaperture.

The separator recited above with respect to the sixth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the sixth aspect of theinvention, wherein said curved surface forms a closed loop about theaperture and extends inwardly into the aperture so as to reduce the areaof the aperture when moving through said aperture from the exterior ofsaid housing towards said inner space.

A separator as recited above in respect of the sixth aspect of theinvention, wherein said curved surface describes a part-circular linewhen viewed in a cross-section taken through a plane coincident with alongitudinal axis through said aperture.

A separator as recited above in respect of the sixth aspect of theinvention, wherein the shoulder comprises a generally cylindrical wall,a free end of which is provided with a circumferential lip which formsthe curved surface.

A separator as recited above in respect of the sixth aspect of theinvention, further comprising a nipple connectable to the shoulder suchthat an internal surface of the nipple combines with the curved surfaceof the shoulder to provide a curved surface to the flow path.

A separator as recited above in respect of the sixth aspect of theinvention, wherein the internal nipple surface meets with the curvedsurface at an edge of the shoulder and, at this meeting point, isoriented tangentially to the curved surface.

A separator as recited above in respect of the sixth aspect of theinvention, wherein the nipple further comprises a curved wall configuredto abut the curved surface of the shoulder.

A separator as recited above in respect of the sixth aspect of theinvention, wherein the nipple is connectable to the shoulder in anyrotational orientation.

A separator as recited above in respect of the sixth aspect of theinvention, wherein the nipple is connectable to the shoulder by spinwelding.

A seventh aspect of the present invention provides a method ofassembling a gas cleaning separator, the method comprising the step ofconnecting a nipple to a shoulder by spin welding; the separator beingas recited above in respect of the sixth aspect of the presentinvention.

An eighth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet; a housing member defining aregion for receiving fluid ejected from the rotor assembly and directingsaid fluid to a first outlet aperture of the housing;

an outlet passage extends between the housing member and the housing forconveying fluid from said region to the exterior of the housing throughsaid outlet aperture, wherein the exterior of said outlet passage isspaced from the housing such that fluid is free to flow about the entireexternal perimeter of said outlet passage.

The separator recited above with respect to the eighth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the eighth aspect of theinvention, wherein the housing member is provided with means forsegregating an inlet to said region from fluid which, in use,re-circulates back towards said inlet after having flowed past saidinlet, wherein said outlet passage extends from said segregating means.

A separator as recited above in respect of the eighth aspect of theinvention, wherein said segregating means comprises a wall, said wallpreferably comprising a free end and being spaced from said housing.

A separator as recited above in respect of the eighth aspect of theinvention, wherein said outlet passage is separate to the housing memberand the housing.

A ninth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises a first inlet for receiving said mixture ofsubstances, a first outlet from which said substances are ejected fromthe rotor assembly during use, and a first flow path for providing fluidcommunication between the first inlet and first outlet, wherein thefirst outlet is positioned more radially outward from said axis than thefirst inlet; and

a housing member located adjacent the rotor assembly, the housing memberand the rotor assembly being spaced from one another so as to provide afirst region therebetween on a first side of the housing member, saidfirst region defining a first fluid flow route for fluid ejected fromthe rotor assembly; the housing member also being spaced from thehousing so as to provide a second region therebetween on a second sideof the housing member, said second region defining a second fluid flowroute for fluid ejected from the rotor assembly;

the rotor assembly further comprises a second inlet which opens intosaid second region on said second side of the housing member, a secondoutlet positioned more radially outward from said axis than the secondinlet, and a second flow path for providing fluid communication betweenthe second inlet and the second outlet.

The separator recited above with respect to the eighth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said second outlet opens into a fluid passageproviding fluid communication between said first outlet and said firstand second regions.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said second outlet opens at location which, withrespect to a flow of said substances ejected from said first outletduring use, is downstream of said first outlet and upstream of saidfirst and second regions.

A separator as recited above in respect of the ninth aspect of theinvention, wherein the second flow path comprises a space between firstand second members of the rotor assembly which each comprise a diskshaped portion, the two members being centred on said axis.

A separator as recited above in respect of the ninth aspect of theinvention, wherein the disk shaped portions of said members each have aradially outer edge of a substantially circular shape, the two membersbeing positioned concentrically with one another.

A separator as recited above in respect of the ninth aspect of theinvention, wherein at least one elongate element is located in saidspace between the first and second members so as to move fluid locatedin said space outwards relative to said axis when, in use, the rotorassembly is rotated about said axis.

A separator as recited above in respect of the ninth aspect of theinvention, wherein each elongate element extends radially along thesecond flow path.

A separator as recited above in respect of the ninth aspect of theinvention, wherein each elongate element is comprised of one of thefirst and second members and abuts the other of the first and secondmembers.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said disk shaped portion of each member isfrusto-conical.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said second flow path comprises a frusto-conicalshape.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said first flow path comprises a frusto-conicalshape.

A separator as recited above in respect of the ninth aspect of theinvention, wherein the second inlet of said second flow path comprisesan annular shape centred on said axis.

A separator as recited above in respect of the ninth aspect of theinvention, wherein the second flow path extends through an aperture inthe housing member between said first and second sides of the housingmember.

A separator as recited above in respect of the ninth aspect of theinvention, wherein the second inlet of said second flow path is definedby a generally cylindrical wall.

A separator as recited above in respect of the ninth aspect of theinvention, wherein a space is provided between a part of the housingmember defining said aperture therein and a first portion of the rotaryassembly defining at least part of said second flow path, and wherein afurther portion of the rotary assembly extends from said first portionso as to cover said space.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said further portion is located on said second sideof the housing member.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said further portion extends from the second inlet.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said further portion has an annular shape.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said further portion has an outer circular perimeteredge of a diameter greater than the diameter of said aperture in thehousing member.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said further portion is planar and oriented in aplane to which said axis is perpendicular.

A separator as recited above in respect of the ninth aspect of theinvention, wherein a surface defining the second flow path and extendingfrom the second inlet has a radially outermost part relative to saidaxis which converges with said axis when moving along said second flowpath from the second inlet towards the second outlet.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said radially outermost part of said second flow pathsurface has a frusto-conical shape.

A separator as recited above in respect of the ninth aspect of theinvention, wherein said frusto-conical shape of said radially outermostpart has a central longitudinal axis coincident with said axis ofrotation.

A tenth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet; and

the rotor assembly further comprising a rotary shaft coincident withsaid axis and mounted to said housing, wherein a first end portion ofthe rotary shaft extends through said housing to a position exteriorlyof said housing and a fluid passageway extends axially through therotary shaft and has an opening positioned exteriorly of said housing;

the rotor assembly further comprises flow control means for controllingfluid entry to said shaft fluid passageway from the exterior of saidhousing, wherein the flow control means comprises means for imparting,onto fluid entering said passageway, a rotary motion along a pathradially outward from the shaft fluid passageway.

The separator recited above with respect to the tenth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the tenth aspect of theinvention, wherein said rotary motion is centred on said axis ofrotation of the rotor assembly.

A separator as recited above in respect of the tenth aspect of theinvention, wherein said passageway is coincident with said axis ofrotation of the rotor assembly.

A separator as recited above in respect of the tenth aspect of theinvention, wherein said means for imparting a rotary motion onto fluidcomprises at least one fluid pathway positioned radially outward fromsaid axis of rotation of the rotor assembly.

A separator as recited above in respect of the tenth aspect of theinvention, wherein said means for imparting a rotary motion onto fluidcomprises a member spaced from said opening of the shaft fluidpassageway, wherein the at least one fluid pathway is an apertureextending through said member.

A separator as recited above in respect of the tenth aspect of theinvention, wherein four of said fluid pathways are positionedequi-distant along the circumference of a circle centred on said axis.

A separator as recited above in respect of the tenth aspect of theinvention, wherein said member is planar and oriented with said axisperpendicular thereto.

A separator as recited above in respect of the tenth aspect of theinvention, wherein the flow control means further comprises at least onedrain aperture positioned more radially outward from said axis than eachfluid pathway.

A separator as recited above in respect of the tenth aspect of theinvention, wherein the flow control means and at least part of a turbinefor driving rotation of the rotor assembly is a unitary component.

A separator as recited above in respect of the tenth aspect of theinvention, wherein a second end portion of the rotary shaft distal tothe first end portion is mounted to the housing.

A separator as recited above in respect of the tenth aspect of theinvention, wherein the fluid passageway extends between the first andsecond end portions of the rotary shaft so as to provide fluidcommunication therethrough between the exterior and interior of thehousing.

A separator as recited above in respect of the tenth aspect of theinvention, wherein the fluid passageway is in fluid communication with abearing by which said second end portion of the rotary shaft is mountedto the housing.

A separator as recited above in respect of the tenth aspect of theinvention, wherein the fluid passageway is in fluid communication withsaid inlet of the rotor assembly.

An eleventh aspect of the present invention provides a method ofassembling a gas cleaning separator for separating a flowable mixture ofsubstances of different densities, such as a gas and liquid; theseparator comprising:

a housing defining an inner space and having an aperture therein forproviding fluid communication between said inner space and the exteriorof said housing, and

a fluid flow passage sealed about said aperture and in fluidcommunication therewith for conveying fluid through said passage andaperture between said inner space and the exterior of said housing;

the method of assembling said separator comprises the step of:

bonding the material of the housing and fluid flow passage togetheralong a closed loop formed by an intersection of abutting surfaces ofthe housing and fluid flow passage.

The separator recited above with respect to the eleventh aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A method as recited above in respect of the eleventh aspect of theinvention, wherein said closed loop is of a circular shape.

A method as recited above in respect of the eleventh aspect of theinvention, wherein said bonding step comprises rotating the housing andfluid flow passage relative to one another whilst said surfaces thereofare in abutment with each other.

A method as recited above in respect of the eleventh aspect of theinvention, wherein said relative rotation of the housing and fluid flowpassage is stopped with the housing and flow passage arranged in arequired position relative to one another so as to allow said abuttingsurfaces to bond to one another.

A method as recited above in respect of the eleventh aspect of theinvention, wherein said bonding step comprises spin welding saidabutting surfaces to one another.

A method as recited above in respect of the eleventh aspect of theinvention, wherein said bonding step comprises applying adhesive to atleast one of said abutting surfaces.

A method as recited above in respect of the eleventh aspect of theinvention, wherein said bonding step comprises ultrasonic welding orvibration welding said abutting surfaces to one another.

A method as recited above in respect of the eleventh aspect of theinvention, wherein the fluid flow passage is a nipple comprising an openend, distal to said abutting surface, for subsequent connection with afurther fluid flow passage, such as a hose.

A twelfth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space and having an aperture therein forproviding fluid communication between said inner space and the exteriorof said housing, and

a fluid flow passage sealed about said aperture and in fluidcommunication therewith for conveying fluid through said passage andaperture between said inner space and the exterior of said housing; andwherein

the material of the housing and fluid flow passage are bonded togetheralong a closed loop formed by an intersection of abutting surfaces ofthe housing and fluid flow passage.

The separator as recited with respect to the twelfth aspect of thepresent invention may include one or more of the following features.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein said closed loop is of a circular shape.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein said bond is made by rotating the housing and fluidflow passage relative to one another whilst said surfaces thereof are inabutment with each other.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein said relative rotation of the housing and fluid flowpassage is stopped with the housing and flow passage arranged in arequired position relative to one another so as to allow said abuttingsurfaces to bond to one another.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein said bond is made by spin welding said abuttingsurfaces to one another.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein said bond is made by applying adhesive to at leastone of said abutting surfaces.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein said bond is made by ultrasonic welding or vibrationwelding said abutting surfaces to one another.

A separator as recited above in respect of the twelfth aspect of theinvention, wherein the fluid flow passage is a nipple comprising an openend, distal to said abutting surface, for subsequent connection with afurther fluid flow passage, such as a hose.

A thirteenth aspect of the present invention provides a method ofassembling a gas cleaning separator for separating a flowable mixture ofsubstances of different densities, such as a gas and liquid; wherein theseparator comprises:

a housing comprising first and second separate parts, the first housingpart having a registration surface against which a datum surface of thesecond housing part registers so as to define an inner space of thehousing; and

a rotor assembly located in said inner space and rotatable about an axisof the first housing part relative to the housing, the rotor assemblycomprising a rotary shaft rotatably mounted to the first housing part bymeans of a bearing unit and rotatably mounted to the second housingpart;

the method of assembling said separator comprises the steps of:

rotatably mounting the rotary shaft to the second housing part in apredetermined position relative to said datum surface wherein saidpredetermined position is coincident with said axis when the datumsurface of the second housing part is in register with said registrationsurface of the first housing part;

locating the bearing unit on a jig wherein the jig comprises a datumsurface for registering with the registration surface of the firsthousing part, and means for receiving said bearing unit in a positionrelative to the datum surface of the jig such that the bearing unit isreceived by the jig in a position relative to the datum surface of thejig which is coincident with said axis when the datum surface of the jigis in register with said registration surface of the first housing part;

locating the datum surface of the jig in register with said registrationsurface of the first housing part; and

secure the bearing unit to the first housing part.

The separator recited above with respect to the thirteenth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A method as recited above in respect of the thirteenth aspect of theinvention, wherein the step of securing the bearing unit comprisesmoving the receiving means of the jig in an axial direction along saidaxis relative to the first housing part whilst the datum surface of thejig is in register with said registration surface of the first housingpart, the bearing unit being thereby brought into abutment with thefirst housing part.

A method as recited above in respect of the thirteenth aspect of theinvention, wherein the receiving means is moved in said axial directionrelative to the datum surface of the jig so as to press the bearing unitagainst the first housing part.

A method as recited above in respect of the thirteenth aspect of theinvention, wherein the jig comprises means for permitting movement ofthe receiving means in an axial direction along said axis relative tothe datum surface of the jig.

A method as recited above in respect of the thirteenth aspect of theinvention, wherein the step of securing the bearing unit comprisesrotating the receiving means of the jig about said axis relative to thefirst housing part whilst the datum surface of the jig is in registerwith said registration surface of the first housing part.

A method as recited above in respect of the thirteenth aspect of theinvention, wherein the step of securing the bearing unit comprises spinwelding the bearing unit to the first housing part.

A method as recited above in respect of the thirteenth aspect of theinvention, wherein the jig comprises means for permitting rotation ofthe receiving means relative to the datum surface of the jig.

A fourteenth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; wherein the separator has beenassembled as recited above in respect of the thirteenth aspect of thepresent invention.

A fifteenth aspect of the present invention provides a method ofassembling a system comprising a gas cleaning separator for separating aflowable mixture of substances of different densities, such as a gas andliquid; wherein the method comprises the steps of selecting a particularversion of a first type of component from a plurality of differentversions of said first type of component; and connecting said particularversion of said first type of component with a second type of component;and wherein

said plurality of different versions of said first type of componentcomprise common features for connecting with said second type ofcomponent.

The separator recited above with respect to the fifteenth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A method as recited above in respect of the fifteenth aspect of theinvention, further comprising the step of selecting a particular versionof said second type of component from a plurality of different versionsof said second type of component.

A method as recited above in respect of the fifteenth aspect of theinvention, further comprising the step of locating a third type ofcomponent between the first and second types of component.

A method as recited above in respect of the fifteenth aspect of theinvention, further comprising the step of selecting said third type ofcomponent from a plurality of different versions of said third type ofcomponent, wherein said plurality of different versions of said thirdtype of component comprise common features for connecting with saidfirst and second types of component.

A method as recited above in respect of the fifteenth aspect of theinvention, wherein said first type of component comprises a rotorhousing; said second type of component comprise a valve unit housing;and said third type of component comprises a heat shield.

A method as recited above in respect of the fifteenth aspect of theinvention, wherein said components are of said separator.

A method as recited above in respect of the fifteenth aspect of theinvention, wherein said plurality of different versions of said firsttype of component comprises further common features for connecting witha fourth type of component.

A method as recited above in respect of the fifteenth aspect of theinvention, wherein said fourth type of component is a nipple.

A sixteenth aspect of the present invention provides a kit of parts forassembling into a gas cleaning separator for separating a flowablemixture of substances of different densities, such as a gas and liquid;wherein said kit of parts comprises a plurality of different versions ofa first type of component of said separator for connecting with a secondtype of component of said separator; and at least one version of saidsecond type of component; said plurality of different versions of saidfirst type of component comprising common features for connecting withsaid second type of component. Ideally, said plurality of differentversions of said first type of component comprises further commonfeatures for connecting with a third type of component.

A seventeenth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; wherein the separator comprises:

a housing defining an inner space;

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing; and

a valve unit for controlling a flow, from an outlet of said housing, ofa substance separated from said mixture of substances, wherein saidvalve unit comprises a valve arrangement located in an inner spacedefined by a valve unit housing; and wherein

the valve unit housing is separate to the rotor assembly housing.

An eighteenth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly located in said inner space and rotatable about an axisrelative to the housing, and

a housing member mounted to said housing so as to allow a flow of fluidto either side of the housing member wherein fluid flowing on one sideof said member is directed by said member towards the exterior of saidhousing through a first outlet aperture in said housing; and wherein

said fluid is directed through an outlet passage connecting said housingmember to the exterior of the housing, the outlet passage being sealedto at least one of the housing member and housing by means of a sealingelement provided about the outlet passage.

The separator recited above with respect to the eighteenth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein said outlet passage is spaced from said housing.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein said outlet passage is separate to the housing memberand sealed thereto by means of a sealing element.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein said outlet passage is separate to the housing andsealed thereto by means of a sealing element.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein each sealing element for sealing said outlet passageis provided on an exterior surface of said passage in abutment with ashoulder defined by said surface.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein said outlet passage is integral with a valve unitlocated exteriorly of the housing for controlling a flow of fluid fromthe housing.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein each sealing element is an O-ring seal.

A separator as recited above in respect of the eighteenth aspect of theinvention, wherein said outlet passage is spaced from said housing so asto allow fluid, located between the housing member and said housing, toflow about the entire outer perimeter thereof.

A nineteenth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, wherein the outlet is positioned more radiallyoutward from said axis than the inlet, and wherein the rotor assemblycomprises a rotary shaft having a longitudinal axis coincident with saidaxis of rotation and a separator disc mounted to the rotary shaft bymeans of an aperture which is provided in the separator disc; andwherein

the rotary shaft comprises at least one spline, and in that the aperturein the separator disc has a shape which corresponds to a cross-sectiontaken perpendicular to the axis through the rotary shaft and the atleast one spline.

The separator recited above with respect to the nineteenth aspect of thepresent invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein the at least one spline is provided on a central hubjoined to the rotary shaft.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein three splines are provided.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein the at least one spline comprises a tip portion,providing a free end to the spline, and a root portion, radially inwardof the tip portion, the root portion having a greater circumferentialdimension than the tip portion.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein the different circumferential dimensions of the rootportion and the tip portion provide a step on either side of the atleast one spline at the junction between the root portion and the tipportion.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein the circumferential dimension of the root portionvaries along an axial length of the at least one spline.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein the separator disc has a frusto-conical shape.

A separator as recited above in respect of the nineteenth aspect of theinvention, wherein the or each spline extends axially along a length ofthe rotary shaft.

A twentieth aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space,

a rotor assembly (for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, the rotor assembly further comprising a rotaryshaft; and wherein

said rotary shaft is provided with a coating of a plastics materialalong a length of said rotary shaft slidably receiving at least onecomponent of said separator.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein at least one of said components is of a metallicmaterial.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein at least one of said components is a helical spring.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein at least one of said components is a bearing unit.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein said rotary shaft receives two of said components onopposite end portions of said rotary shaft, wherein each component is ahelical spring.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein each helical spring is compressed between the rotorassembly and a different one of two bearing units connecting the rotaryshaft to the housing.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein each helical spring is of a metallic material.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein said rotary shaft is of a non-hardened material.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein said material is non-hardened metal, and preferablynon-hardened steel.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein the rotor assembly comprises at least one elementextending from said rotary shaft, wherein said element is of the samematerial as said coating and formed integrally therewith.

A separator as recited above in respect of the twentieth aspect of theinvention, wherein said coating and said at least one element areinjection moulded onto said rotary shaft and thereby formedsimultaneously with one another.

A twenty-first aspect of the present invention provides a gas cleaningseparator for separating a flowable mixture of substances of differentdensities, such as a gas and liquid; the separator comprising:

a housing defining an inner space, and

a rotor assembly for imparting a rotary motion onto said mixture ofsubstances, the rotor assembly being located in said inner space androtatable about an axis relative to the housing, wherein the rotorassembly comprises an inlet for receiving said mixture of substances, anoutlet from which said substances are ejected from the rotor assemblyduring use, and a flow path for providing fluid communication betweenthe inlet and outlet, and wherein

the separator further comprises an electric motor for rotating saidrotor assembly, and a fluid passageway through the electric motor forreceiving, in use, a substance separated from said mixture ofsubstances.

The separator recited above with respect to the twenty-first aspect ofthe present invention may include one or more of the following featuresand/or limitations.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said fluid passageway through the electric motoris defined, at least in part, by a rotor and a stator of the electricmotor.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said fluid passageway comprises a space betweenthe rotor and the stator of the electric motor.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said rotor is connected to the rotor assembly.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein electrical leads located in said fluid passagewayare sealed in an insulating material.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said insulating material is provided as a layercovering electrical leads of said stator.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said insulating material comprises an epoxylacquer.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein the electric motor comprises one or moreelectronic components sealed from said fluid passageway through theelectric motor.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein the separator comprises a housing in which theelectric motor is located.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said electric motor housing is connected to andis separable from the housing in which the rotor assembly is located.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein the electric motor housing comprises acompartment sealed from said fluid passageway and in which electroniccomponents of the electric motor are located.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said compartment has a generally annular orpart-annular shape which, in the assembled separator, is concentric withsaid rotor assembly.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said compartment is enclosed by said electricmotor housing and by a member separate to the said housing and sealedthereto.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said member is of a generally annular orfrusto-conical shape.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said member is arranged concentrically with saidrotor assembly.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein a radially inner portion of said member is sealedto said electric motor housing along a closed loop and a radially outerportion of said member is sealed to said electric motor housing along afurther closed loop.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said radially inner portion of said member issealed to a generally cylindrical portion of said electric motor housinginto which, in the assembled separator, said rotor assembly extends.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said radially inner portion of said memberdefines an aperture having a diameter less than or substantially equalto the innermost diameter of the stator of the electric motor.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said member is provided with at least oneaperture through which an electrical lead extends and to which said leadis sealed.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said one or more electronic components compriseone or more components for controlling the operation of the electricmotor.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein said fluid passageway is in fluid communicationwith an outlet port in the electric motor housing.

A separator as recited above in respect of the twenty-first aspect ofthe invention, further comprising an electrical connector for receivingan electrical lead providing electrical power and/or control signals tothe electric motor.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein the electrical connector is electricallyconnected to the electric motor by means of one or more electriccomponents.

A separator as recited above in respect of the twenty-first aspect ofthe invention, wherein the electrical connector is located in anaperture extending through a portion of a housing of the separator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional perspective view of a prior art ALFDEX™centrifugal separator;

FIG. 2 is a cross-sectional side view of the separator shown incombination with a turbine casing;

FIG. 3 is a cross-sectional perspective view of an inlet/outlet nipplefor use with the separator shown in FIG. 1;

FIG. 4 is a cross-sectional side view of a mould for the inlet/outletnipple shown in FIG. 3;

FIG. 5 is a perspective view of a rotor of the separator shown in FIG.1;

FIG. 6 is a cross-sectional perspective view of the rotor shown in FIG.5;

FIG. 7 is perspective end view of the rotor shown in FIG. 5, wherein anupper rotor disc is shown removed from a rotary shaft of said rotor suchthat the rotary shaft is shown in cross-section;

FIG. 8 is a cross-sectional side view of the separator shown in FIG. 1,wherein the flow paths of separated gas and oil are illustrated;

FIGS. 9 and 10 are cross-sectional side views of the separator shown inFIG. 1, wherein a desirable flow path of oil and an undesirable flowpath of oil are respectively illustrated;

FIG. 11 is a perspective top view of a housing insert of the separatorshown in FIG. 1;

FIG. 12 is a perspective side view of the housing insert shown in FIG.11, wherein a portion of an outer skirt of the housing insert has beenremoved so as to more clearly show an undesirable flow path of separatedoil droplets;

FIG. 13 is a perspective side view of a first separator according to thepresent invention, wherein a housing of the separator is shown incross-section so as to illustrate a rotor assembly and housing insertlocated within said housing;

FIG. 14 is an enlarged view of the area encircled by line A shown inFIG. 13;

FIG. 15 is a cross-sectional perspective side view of the firstembodiment of the present invention as shown in FIG. 13;

FIG. 16 is a cross-sectional side view of an inlet nipple connected toan inlet in the first embodiment;

FIG. 17 is a perspective view of the inlet nipple and inlet of FIG. 16separated from one another;

FIG. 18 is a cross-sectional perspective top view of the firstembodiment of FIG. 13, wherein the cross-section is taken through aplane parallel with a bearing plate of the first embodiment and passingthrough the line 18-18 shown in FIG. 15;

FIG. 19 is a cross-sectional perspective side view of a secondembodiment, wherein the second embodiment differs from the firstembodiment in that a covering of plastics material is provided on theupper end of the rotor assembly;

FIG. 20 is a cross-sectional perspective side view of the firstembodiment shown in FIG. 13;

FIG. 21 is a perspective top view of an upper rotor disc and rotaryshaft of the first embodiment shown in FIG. 13;

FIG. 22 is a velocity flow diagram showing the velocity of inlet fluidrelative to a guide surface provided on the upper rotor disc shown inFIG. 21;

FIG. 23 is a perspective bottom view of the upper rotor disc and rotaryshaft shown in FIG. 21;

FIG. 24 is a perspective bottom view of one of a plurality of separatordiscs for slidably locating on the rotary shaft shown in FIGS. 21 and23;

FIG. 25 is a perspective bottom view of the separator disc shown in FIG.24 being slidably located on the rotary shaft shown in FIGS. 21 and 23;

FIG. 26 is a perspective view of a fan disc and associated end platelocated above a housing insert which, in turn, is located on a bearingplate of the first embodiment shown in FIG. 13;

FIG. 27 is a perspective side view of a plurality of separator discslocated on the rotary shaft of FIGS. 21 and 23, wherein said discs andshaft are assembled with the components shown in FIG. 26;

FIG. 28 is a perspective top view of a housing insert of the firstembodiment shown in FIG. 13, wherein the housing insert is shown inisolation of other components except for an oil splash guard locatedbelow said insert;

FIG. 29 is a partial perspective bottom view of the first embodimentshown in FIG. 13, specifically showing a turbine wheel assembly of saidembodiment;

FIG. 30 is a partial cross-sectional perspective side view of theturbine wheel assembly shown in FIG. 29;

FIG. 31 is a partial cross-sectional perspective side view of analternative turbine wheel assembly to that shown in FIGS. 29 and 30;

FIG. 32 is a perspective bottom view of the turbine wheel assembly shownin FIG. 31;

FIG. 33 is a cross-sectional side view of the first embodiment shown inFIG. 13;

FIG. 34 is an enlarged cross-sectional side view of the first embodimentshown in FIG. 13, wherein the flow paths of gas and separated oildroplets through the separator are illustrated;

FIG. 35 is a cross-sectional side view of an electric motor drivearrangement to that shown in the above Figures, wherein the electricmotor drive arrangement is shown in use with the prior art separator ofFIG. 1;

FIG. 36 is a schematic view showing the modular nature of the separatorsystem shown in FIG. 13;

FIGS. 37 and 38 are views of a top bearing unit of the first embodimentbeing mounted to a spin welding jig;

FIG. 39 is a perspective side view of a top bearing unit mounted to thespin welding jig of FIGS. 37 and 38;

FIG. 40 is a perspective view of the assembly shown in FIG. 39 locatedwithin the interior of a rotor housing of the first embodiment prior toa spin welding of a top bearing unit to the interior of said housing;and

FIG. 41 is a perspective view of a top bearing unit having been attachedto an interior surface to the housing shown in FIG. 40 by means of aspin welding operation.

DETAILED DESCRIPTION

The prior art ALFDEX™ separator will now be described with reference toFIGS. 1 to 12 of the accompanying drawings and with particular emphasisbeing placed on those aspects of this prior art separator that have beenimproved by the inventors.

A number of views of an assembled prior art ALFDEX™ separator 2 areshown in FIGS. 1, 2, 8, 9 and 10. It will be understood by those skilledin the art that the prior art separator 2 comprises a generallycylindrically shaped rotor housing 4 for receiving a number of internalcomponents which function to separate oil from vented gas directed intosaid rotor housing 4.

One end of the cylindrical housing 4 is provided with an upstandingannular shoulder 6, which defines a fluid inlet 8 to the separator 2. Itwill be understood therefore that gas vented from a crank case, andrequiring the removal of oil therefrom, enters the separator 2 via thefluid inlet 8.

An aperture 10 in a cylindrical wall of the rotor housing 4 provides anoutlet for cleaned gas to pass from the interior of the rotor housing 4into a further housing 12 associated with a valve unit 14 (see FIG. 1).The valve unit 14 comprises a valve arrangement for controlling the flowof cleaned gas from the separator 2. Details of the operation of thevalve unit 14 will not be described herein. However, as will be evidentfrom FIG. 1, the exterior of the rotor housing 4 is designed to matewith the housing 12 of the valve unit 14 so that the two housings 4,12combine to define an internal space between said housings 4,12 suitablefor receiving the internal components of the valve unit 14. The twohousings 4,12 are secured to one another by conventional screw threadedfastenings 16. It will be appreciated therefore that a particular valveunit housing 12 can only be used with a specific rotor housing 4 havingthe necessary mating features.

With reference to FIG. 1, it will be seen that the housing 12 of thevalve unit 14 is provided with an upstanding annular shoulder 18 thatdefines a fluid outlet through which cleaned gas passes from theseparator 2. The annular shoulder 18 provided on the valve unit housing12 is substantially similar to the annular shoulder 6 provided on therotor housing 4. Due to their similarity, the inlet and outlet shoulders6,18 may interchangeably receive inlet/outlet nipples having the sameinterface profile. One such nipple 22 having a 90° bend is shown, incross-section, in FIG. 3. One end of the nipple 22 is provided with anannular collar 24 defining an annular recess 26. The annular recess 26has a square-edge profile and a diameter allowing it to receive ahousing annular shoulder 6,18 (which also has a square edge) in abutmenttherewith.

The interface of the shoulder 6 of the rotor housing 4 with an inletnipple 28 can be seen with reference to FIG. 2 of the accompanyingdrawings. It will be appreciated that the nipple 28 shown in FIG. 2 hasa different bend angle than the nipple 22 shown in FIG. 3.

The inlet/outlet nipples are secured to their respective housings 4,12by clamping them onto the housing shoulders 6,18 using an annular washer30, which presses down on the shoulder 24 of a nipple 22,28 when screwthreaded fasteners 32 are threadedly engaged with two threaded bosses34. The two bosses 34 are upstanding from the relevant housing 4,12 andlocated on either side of the annular shoulder 6,18.

An O-ring seal 36 is located, trapped and compressed between the recess26 and the housing shoulder 6,18 so as to prevent an undesirable leakingof fluid from the interface between the inlet/outlet nipple andrespective housing (see FIG. 2 in respect of the inlet nipple).

With further reference to the nipples 22,28 shown in FIGS. 3 and 2respectively, a second end of the nipple (distal to the end providedwith the interface profile) is provided with teeth or serrations 38 onan exterior surface thereof for gripping a hose which, in use, islocated over the nipple second end.

The fluid flow paths provided by the two nipples 22,28 each comprise abend having an inner corner 40 substantially lacking a radius. In theprior art separator 2, angled nipples are manufactured using injectionmoulding (for plastics nipples) and die casting (for aluminium nipples)techniques. As will be readily understood from FIG. 4 (which shows themoulding of a nipple 22), in order to allow removal of first and secondinternal moulding segments 42,44 in the directions indicated by firstand second arrows 46,48 respectively, it is not possible for the mouldsegments 42,44 to provide a radius to the inner corner 40.

The aforementioned internal components housed by the rotor housing 4will now be described in greater detail with particular reference toFIG. 8.

A top bearing unit 50 is secured to an inner surface of the rotorhousing 4 immediately downstream of the fluid inlet 8. The top bearingunit 50 comprises caged bearings 52 trapped between an upper steel capmember 54 and a lower bearings seat member 56 of a plastics material.The bearing unit 50 is manufactured by moulding the lower bearings seatmember 56 around the upper steel cap member 54 with the caged bearings52 retained securely therebetween. The arrangement of the top bearingunit 50 is most clearly shown in FIG. 8, although it is also shown inFIGS. 2 and 9 in the context of the prior art separator 2.

The bearings seat member 56 has a circular shape and a downwardlyprojecting cylindrical wall 58 (encasing a lower part of the cap member54) which, in the assembled separator 2, abuts laterally against acylindrical wall 60 of the rotor housing 4. The abutment with thecylindrical wall 60 assists in ensuring a correct lateral positioning ofthe top bearing unit 50 relative to the rotor housing 4. A secondcylindrical wall 62 of the rotor housing 4 is positioned radiallyinwardly of the first cylindrical wall 60 so as to ensure a correctaxial positioning of the top bearing unit 50 relative to the rotorhousing 4. The top bearing unit 50 is secured to the rotor housing 4 bymeans of three threaded fasteners (not shown). The arrangement of theseparator 2 is such that the rotary axis of the top bearing unit 50 iscoincident with a central axis 64 of the rotor housing 4.

Three part-circular slots 66 (only two of which are shown in FIG. 8) areprovided in the top bearing unit 50 so as to allow a flow of inlet fluidtherepast (as shown by arrow 68). The upper cap member 54 deflects inletfluid from the caged bearings 52, however as will be understood by thoseskilled in the art, the underside of the uppermost part of the capmember 54 also deflects (into the caged bearings 52) a lubricating oilmist which travels upwardly through a rotor shaft and into the topbearing unit 50 during use.

The remaining internal components of the separator 2 are assembledseparately to the rotor housing 4 and are then located within thehousing 4 as a unitary assembly. The unitary assembly comprises a firstgroup of components which, in use of the separator 2, remains stationaryrelative to the rotor housing 4, and a second group of components which,in use of the separator 2, rotates about the central axis 64 relative toboth the rotor housing 4 (and the valve unit housing 12) and the firstgroup of components.

The first group of components comprises an annular-shaped bearing plate70 and a dish-shaped member 72, known as a housing insert. The housinginsert 72, in combination with the bearing plate 70, function tosegregate separated oil from cleaned gas prior to the separated oil andcleaned gas exiting the rotor housing 4. The bearing plate 70 is made ofsteel and the housing insert 72 is made of a plastics material. Thebearing plate 70 and housing insert 72 are secured to one another bymeans of three screw threaded fasteners 74 (only one of which is shownin FIG. 1 of the accompanying drawings) which threadedly engage bosses76 projecting downwardly from an underside of the housing insert 72.This first group of components will be discussed in greater detail laterin this description.

The second group of components form a rotor assembly and comprises arotary shaft 78, an upper rotor disc 80, a plurality of individualseparator discs 82 which together form a stack 84 of separator discs 82,an end plate 86, and a combined fan and turbine unit 88. The componentsof this second group are secured to one another in such a way as toprevent their rotation relative to one another. The second group ofcomponents is, however, rotatably mounted to the first group ofcomponents by means of a bottom bearing unit 90 (see FIG. 10 inparticular).

The rotor assembly formed by the second group of components will now bedescribed in more detail.

The rotary shaft 78 is made of a metallic material and has an annularcross-section so as to provide a longitudinally extending fluid flowpath 92 along its entire length. In use of the separator 2, this flowpath 92 allows an oil mist to be transported from a turbine casingupwardly through the rotary shaft and into the top bearing unit 50 so asto lubricate the bearings of said unit 50. A restrictor element 93 inthe form of an annular disc (with a cylindrical wall upstanding from aradially outer circumferential edge thereof) is located on an upwardlyfacing internal shoulder of said fluid flow path 92 at an upper end ofthe rotary shaft 78. The restrictor element 93 functions to reduce theflow path area through the rotary shaft 78 (thereby providing a nozzle)at an outlet from the rotary shaft 78 into the top bearing unit 50.

The exterior of the rotary shaft 78 is provided with a number ofrecesses and shoulders for receiving circlips which assist in retainingcomponents in the correct axial position on the rotary shaft 78. Onesuch circlip 94 is clearly shown in FIG. 6 as providing an upwardlyfacing shoulder against which a washer 95 abuts. A helical compressionspring 96 abuts an upwardly facing shoulder of the washer 95. Thecircumferential recess in which the circlip 94 is located has sufficientwidth (i.e. the dimension of the recess in the axial direction) to allowthe circlip 94 to move axial along the rotary shaft 78 (within therecess). This allows the spring 96 to apply an axial force to the bottombearing unit 90.

Other recesses are provided on the exterior surfaces of the rotary shaft78 for locating and retaining components on said shaft 78.

Each of the upper rotor disc 80, separator discs 82, and end plate 86has a frustoconical part (defining an upper frusto-conical surface 102)with a plurality of spoke members extending radially inwardly therefromto a hub element which, in use, is located about the rotary shaft 78.

Whilst the spoke members of the upper rotor disc 80 and separator discs82 have open spaces between them to allow for a flow of fluid axiallytherethrough along the rotary shaft 78, the spoke members of the endplate 86 are joined to one another at their lower surfaces so as toprevent an axial flow of fluid along the rotary shaft 78 either upwardlypast the end plate 86 or downwardly past the end plate 86.

The frusto-conical geometry of the upper rotor disc 80 and end plate 86is substantially identical to that of the separator discs 82 so as toallow the upper rotor disc 80 and end plate 86 to be stacked with theseparator discs 82, wherein the upper rotor disc 80 is located at thetop of the separator disc stack 84 and the end plate 86 is located atthe bottom of the separator disc stack 84. Furthermore, whilst theseparator discs 82 will be understood by the skilled person to becomparatively thin so as to allow a large number of discs to be providedin a relatively short stack 84, the upper rotor disc 80 and end plate 86are considerably thicker than the separator discs 82 so as to providerigidity at either end of the disc stack 84 and thereby allow acompressive axial force to be uniformly applied to the frusto-conicalparts of the separator discs by the upper disc 80 and end plate 86. Thecompressive force is, more specifically, generated by the helicalcompression spring 96 which presses upwardly on the underside of the hub98 of the end plate 86.

Regarding the compression of the disc stack 84 between the upper disc 80and the end plate 86, it will be understood by the skilled person thatadjacent separator discs 82 within the stack 84 must remain spaced fromone another in order to allow a flow of fluid through the separator 2.This spacing of the separator discs 82 is provided by means of aplurality of ribs 100 (known as caulks) provided on the upper surface ofthe frusto-conical part of each separator disc 82. Each caulk 100extends from a radially inner edge 104 of said upper surface 102 to aradially outer edge 106 of said surface. The caulks 100 stand proud ofsaid upper surface 102 and, in the assembled stack 84 of separator discs82, abut the underside of the above adjacent disc. As understood by aperson skilled in the art, each separator disc 82 is locatable on therotary shaft 78 in one of only six possible angular positions relativeto the rotary shaft 78, and the positioning of the caulks 100 on saidupper surface 102 is such that the caulks of adjacent discs 82 mustalign with one another when the discs 82 are arranged in any of thesesix positions. As a result, the compression force applied to the discstack 84 by the end plate 86 is transmitted through the stack 84 bymeans of the aligned caulks 100 without the spacing between adjacentseparator discs 82 closing.

With further regard to the compression force applied to the separatordisc stack 84, it will be understood by the skilled person that thisforce is generated by the helical compression spring 96 and applied tothe end plate hub 98. Due to the rigidity of the end plate 86, thecompression force is transmitted from the hub 98 to the frustoconicalpart 108 of the end plate 86 via a plurality of radially extendingspokes 110 of the end plate 86. The compression force is thentransmitted to the disc stack 84 via the frusto-conical part 108, andtransmitted upwardly through the stack 84 (via the caulks 100) to thefrusto-conical part 112 of the upper rotor disc 80. The compressionforce is transmitted from the frusto-conical part 112 to the hub 114 ofthe upper rotor disc 80 via six radially extending spokes 116. Thecompression force is transmittable from the frusto-conical part 112 tothe hub 114 due to the rigidity of the upper rotor disc 80. An axialmovement of the upper rotor disc 80 upwards along the rotary shaft 78 inreaction to the compression force is prevented by a locating of theupper rotor disc hub 114 in a circumferential recess 118 in the exteriorsurface of the rotary shaft 78 (see FIG. 6 in particular). Frictionalforces between the hub 114 and the exterior surface of the rotary shaft78 prevent relative rotation therebetween.

It will be seen from FIGS. 6 and 8 in particular that the hub 114 of theupper rotor disc 80 extends axially downwardly along the rotary shaft 78to a point just above the end plate hub 98. More specifically, the hub114 extends along the full depth of the separator disc stack 84 andthereby separates the hub 120 of each separator disc 82 from the rotaryshaft 78 (see FIG. 7). The hub 120 of each separator disc 82 has ahexagonal shape defining a hexagonal aperture through which the rotaryshaft 78 and upper rotor disc hub 114 extend. Rotational movement of theseparator disc hub 120 relative to the upper rotor disc hub 114 (and,therefore, relative to the rotary shaft 78) is prevented by means of sixsplines 122 which are provided axially along the length of the upperrotor disc hub 114 and extend radially into six corners of the hexagonalaperture defined by the separator disc hub 120. This location of thesplines 122 prevents lateral and rotational movement of a separator dischub 120 relative to the rotary shaft 78.

The separator disc hub 120 of each separator disc 82 is connected to thefrusto-conical part 124 of each separator disc 82 by means of twelveradially extending spokes 126. The spokes 126 (and indeed the remainderof the associated separator disc 82) are made of a relatively thin andresiliently flexible plastics material. However, the spokes 126 arenevertheless capable of resisting the lateral and rotational forces towhich they are subjected without deforming. It will be understood by theskilled person that the compression force generated by the helicalspring 96 is transmitted through the separator disc stack 84 via thecaulks 100 rather than by the separator disc spokes 126.

It will also be understood by the skilled person that the relativegeometry of the splines 122 and the hexagonal hub 120 of each separatordisc 82 ensures that, as mentioned above, each separator disc 82 islocatable on the rotary shaft 78 in one of only six angular positions.However, the polar or angular positions of the caulks 100 of theseparator discs 82 are the same regardless of which of the six angularpositions is used and, accordingly, there is no possibility of theseparator disc stack 84 being assembled on to the rotary shaft 78 withthe caulks 100 of adjacent separator discs 82 being misaligned.

For the purposes of clarity, certain Figures of the accompanyingdrawings show a disc stack with a reduced number of separator discspresent. With specific regard to the prior art separator 2, FIGS. 1, 2,8, 9 and 10 have been simplified in this way.

As shown in FIG. 5, a second circumferential recess 128 is provided inan upper end of the rotary shaft 78 at a location above the first recess118. The second recess 128 receives a second helical compression spring130. The position of the second recess is such that, in the assembledprior art separator 2, the lower end of the second spring 130 is spacedfrom the hub 114 of the upper rotor disc 80 (see FIG. 6) and isprevented from downward axial movement along the rotary shaft 78 by anupward facing shoulder formed by the second recess 128. Furthermore, inthe assembled separator 2, the cage of the caged bearings 52 abuts anddownwardly compresses the second spring 130 (with the upper end of therotary shaft 78 remaining spaced from the cap member 54 of the topbearing unit 50—see FIG. 8 in particular). The second spring 130 appliesa load to the top bearing unit 50 and thereby reduces vibrations andassociated wear at the top bearing unit 50.

All but the combined fan and turbine unit 88 of the second group ofinternal components are shown assembled in FIG. 6 of the accompanyingdrawings. Before the fan/turbine unit 88 is mounted to the lower end ofthe rotary shaft 78, the lower end of the shaft 78 is located through acentral circular aperture provided in each of the bearing plate 70 andhousing insert 72 of the first group of internal components. In sodoing, the lower end of the rotary shaft 78 is also extended through thebottom bearing unit 90 which is secured to the central aperture of thebearing plate 70 (see FIGS. 8 and 10 in particular).

The combined fan and turbine unit 88 is secured to the lower end of therotary shaft 78 which projects downwardly from the underside of thebearing plate 70. The fan/turbine unit 88 is retained in position on thelower end of the rotary shaft 78 by means of a second circlip 132(retained in a third circumferential recess in the shaft 78) and asecond washer 133 abutting an upwardly facing surface of the secondcirclip 132. The axial positioning of the fan/turbine unit 88 on therotary shaft 88, as determined by the second circlip 132, results in anupper surface the unit 88 being pressed into abutment with a deflectorwasher 139 which, in turn, is pressed into abutment with the bottombearing unit 90. In the assembled separator 2, the inner race of thebottom bearing unit 90 abuts the first circlip 94 and presses thiscirclip 94 upwardly against the bias of the first compression spring 96.The pressing of the inner race, deflector washer 139 and fan/turbineunit 88 against the second circlip 132 is such as to retain theseelements in a fixed rotational position relative to the rotary shaft 78.

The rotor assembly of the separator 2 is rotated in a directionindicated by arrow 134 (see FIG. 1) by means of a hydraulic impulseturbine. The fan/turbine unit 88 comprises a Pelton wheel 136 having aplurality of buckets 138 evenly spaced along the circumference thereof.In use of the separator 2, a jet of oil is directed from a nozzle (notshown) within the turbine casing 178 towards the circumference of thePelton wheel 136. More specifically, the jet is directed along a tangentto a circle passing through the plurality of buckets 138 so that the jetenters a bucket aligned with a surface thereof. The jet flows along saidsurface following the internal profile of the bucket and is thereafterturned by said profile to flow along a further surface and be thereafterejected from the bucket. The result is that the jet rotates the wheel136.

A fan having a plurality of blades 140 is also integrally formed withthe wheel 136. The blades 140 are located on the wheel 136 in closeproximity to the underside of the bearing plate 70. The plurality of fanblades 140 are also in approximately the same axial position along therotary shaft 78 as the bottom bearing unit 90. The fan blades 140 extendradially outward from adjacent the bottom bearing unit 90. It will beunderstood by those skilled in the art that the fan blade 140 rotateabout the central axis 64 as the turbine wheel 136 is rotated. In sodoing, the fan blades 140 effectively throw fluid from the regionbetween the wheel 136 and the underside of the bearing plate 70, therebyreducing the fluid pressure in the region of the bottom bearing 90 anddrawing separated oil from a location above the bearing plate 70downward through the bottom bearing unit and into the turbine casing 178below the bearing plate 70.

For ease of manufacture, the wheel 136 is made in upper and lower parts142,144 and pressed into abutment with one another at line 146 as shownin FIG. 8 of the accompanying drawings.

With regard to the first group of internal components, the bearing plate70 is made of steel and has a circular shape with a diametersubstantially equal to the diameter of the rotor housing 4. The relativegeometries are such as to allow the bearing plate 70 to locate on adownwardly facing shoulder 148 at a lower end of the rotor housing 4. Inthis way, the lower open end of the rotor housing 4 is closed by thebearing plate 70. The bearing plate 70 is also provided with a centralcircular aperture which, in the assembled separator 2, is concentricwith the rotor housing 4. In other words, in the assembled separator 2,the circular central aperture of the bearing plate 70 is centered on thecentral axis 64 of the rotor housing 4. Furthermore, as will beparticularly evident from FIG. 1 of the accompanying drawings, thebottom bearing unit 90 is received in the central aperture of thebearing plate 70. The radially outermost part of the bottom bearing unit90 is fixed relative to the bearing plate 70. The radially innermostpart of the bottom bearing unit 90 is located adjacent the rotary shaft78, but is not fixed thereto.

As mentioned above the first group of internal components also comprisesa housing insert 72 which is fixedly secured to the bearing plate 70.The housing insert 72 functions to segregate cleaned gas from oil whichhas been separated therefrom and to provide an outlet 150 for cleanedgas, which connects with the outlet aperture 10 of the rotor housing 4(see FIG. 1 in particular). The housing insert 72 is provided as aunitary moulding of plastics material. However, in describing thehousing insert 72 below, the insert will be considered as comprisingfour portions: an outer cylindrical wall/skirt portion 152; a ditchportion 154; a frusto-conical portion 156; and an outlet portion 158defining said insert outlet 150.

The cylindrical skirt portion 152 of the housing insert 72 has anoutermost external diameter which is substantially equal to the diameterof an interior wall portion of the rotor housing 4 with which the skirtportion 152 abuts. A circumferential recess 159 (see FIG. 12) isprovided in the exterior surface of the skirt portion 152 for receivingan O-ring seal 160 which, in the assembled separator 2, ensures a fluidseal between the housing insert 72 and the rotary housing 4.

The lower end of the cylindrical skirt portion 152 abuts the upper sideof the bearing plate 70 and is provided with a circumferential recess162 (see FIG. 12) for receiving a second O-ring seal 164. It will beunderstood that the second O-ring seal 164 ensures a fluid seal betweenthe housing insert 72 and the bearing plate 70.

A second cylindrical wall positioned radially inwardly of the outerskirt portion 152 and arranged concentrically therewith is connected atits lower end to the skirt portion 152 to form the ditch portion 154.The ditch portion 154, together with the outer skirt portion 152, formsan annular ditch (or gutter) 166 running along the internal cylindricalwall of the rotor housing 4. The ditch 166 has a U-shaped cross-sectionand, during use of the separator 2, collects separated oil dropletswhich are thrown from the separator discs 82 and run downwards on theinterior of the rotor housing 4 under the action of gravity (and underthe action of a downwards spiralling gas flow, as is mentioned in moredetail herein). The ditch portion 154 is provided with four drain holes168 (see FIG. 11 in particular) through which oil collected in the ditch166 may flow so as to pass into a region enclosed by an underside of thehousing insert 72 and an upperside of the bearing plate 70 during use ofthe separator 2.

The third portion 156 of the housing insert 72 has a frusto-conicalshape and is suspended from the ditch portion 154. The frusto-conicalportion 156 is provided with a central circular aperture which, in theassembled separator 2, has a central axis coincident with the centralaxis 64 of the rotor housing 4. An elongate recess 170 (see FIG. 11) isprovided in the upper surface of the frusto-conical portion 156. Thisrecess 170 defines a fluid pathway for cleaned gas which joins with theoutlet portion 158 of the housing insert 72. The flow pathway providedby the recess 170 begins at an upstream end thereof with a downward step172 from the upper surface of the frusto-conical portion 156. Side walls174,176 of the recess 170 increase in height in the downstream directionas the fluid pathway progresses outward from the centre of the housinginsert 72. As will be evident from the top view of the housing insert 72provided by FIG. 11, the recess 170 provides a straight fluid pathwayhaving a length approximately equal to half the diameter of the housinginsert 72.

The outlet portion 158 of the housing insert 72 is provided in the formof a generally cylindrical tube which extends across the ditch 166between apertures in the outer skirt portion 152 and the ditch portion154.

A view of the separator 2 secured to a turbine casing 178 is shown inFIG. 2. The separator 2 is secured to the turbine casing 178 by means ofthree threaded fasteners 180, each of which passes through one of threebosses integral with the lower end of the rotor housing 4. Only onefastener 180 and boss 182 is shown in the cross-sectional side view ofFIG. 2. It will be understood from FIG. 2 by those skilled in the artthat the bearing plate 70 (and, therefore, all of the components of thefirst and second groups) is retained in the required position relativeto the rotor housing 4 by virtue of the turbine casing 178 pressing thebearing plate 70 into abutment with the downwardly facing shoulder 148when the rotor housing 4 and turbine casing 178 are fastened to oneanother. The bearing plate 70 is essentially clamped between the rotorhousing 4 and the turbine casing 178 by means of the threaded fasteners180. As the threaded fasteners 180 are tightened and the bearing plate70 is brought into abutment with the shoulder 148 as a consequence, thesecond helical compression spring 130 is compressed by the top bearingunit 50.

In operation of the separator 2, a nozzle (not shown) in the turbinecasing 178 directs a jet of oil onto the turbine wheel 136 so as torotate the turbine wheel in the direction indicated by arrow 134, aspreviously described in relation to FIG. 1. This rotation of the turbinewheel drives a rotation of the rotor assembly as a whole in thedirection of arrow 134 about the central axis 64 of the rotor housing 4.In other words, the rotary shaft 78; the upper rotor disc 80; the stack84 of separator discs 82; the end plate 86; and the combined fan andturbine unit 88 (i.e. collectively referred to herein as the rotorassembly) rotate together as a unitary assembly within the rotaryhousing 4 and relative to said housing 4 and the bearing plate 70; thehousing insert 72; and the turbine casing 178.

Gas vented from the engine crank casing, and requiring treatment by theseparator 2, is introduced into the separator 2 via the fluid inlet 8located at the top of the rotor housing 4. As indicated by arrow 68 inFIG. 8, the inlet gas enters the rotor housing 4 in a direction parallelwith, and in line with, the central axis 64 and flows through threeslots 66 in the top bearing unit 50 before flowing past the six spokes116 of the upper rotor disc 80. The rotational movement of the sixspokes also results in a lateral movement of the fluid located betweensaid spokes in that said fluid moves tangentially from the circular pathof the spokes 116 and is effectively thrown outwards towards thecylindrical wall of the rotor housing 4. In essence, the six spokes 116impart a cylindrical motion onto the inlet gas.

As inlet gas flows downwardly through the spokes 116,126 of the upperrotor disc 80 and the separator discs 82, the gas is moved laterallytowards the cylindrical wall of the rotor housing 4 via the spacesbetween adjacent separator discs 82, as shown by arrows 184 in FIG. 8.The caulks 100, together with frictional forces applied by the separatordiscs 82, impart a lateral movement on to the fluid located in the discstack 84, which results in said fluid moving outwardly towards thecylindrical wall of the rotor housing 4. This movement of fluid, causedby the rotation of the disc stack 84, is a primary mechanism by whichfluid is drawn into the separator 2.

It will be understood by those skilled in the art that oil droplets 186tend to collect together and form larger droplets at the perimeter ofthe disk stack 84. In this regard, capillary forces acting on smalleroil droplets (due to the small spacing between adjacent separator discs82) tend to prevent small droplets from being thrown from the disc stack84. However, as more oil is moved across a separator disc, the smallerdroplets collect together at the perimeter and form larger dropletshaving a sufficient mass (and associated “centrifugal” force) toovercome the capillary force. The oil is then thrown onto thecylindrical wall of the rotor housing 4. Once received by saidcylindrical wall, the oil droplets 186 tend to run downwardly under theaction of gravity, and the flow of gas through the separator 2, into theannular ditch 166. The outer most circumferential edge of the separatorstack 84 is sufficiently inwardly spaced from the cylindrical wall ofthe rotor housing 4 so as to allow oil droplets to run unimpeded by theseparator discs 82 downwardly into said ditch 166. The O-ring seal 160ensures oil droplets flow into the ditch 166, rather than between thehousing inserts 72 and the rotor housing 4 with the possible consequenceof contaminating clean gas flowing through the outlet 150 of the housinginsert 72 (as will be most readily understood with reference to FIG. 1).

Oil droplets 186 collecting in the ditch 166 are drained therefromthrough the four drain holes 168. This draining action is assisted bythe fluid pressure gradients within the rotor housing 4 and turbinecasing 178. More specifically, it will be understood by those skilled inthe art that, because of the rotary motion of the rotor assembly, thefluid pressure within the rotor housing 4 is greater at the peripheraledge of the separator disc stack 84 than in the region between theunderside of the housing insert 72 and the upperside of the bearingplate 70. As a consequence, there tends to be a flow of cleaned gasdownwards through the drain holes 168. This fluid flow tends to pushseparated oil droplets along the annular ditch 166 and downwards throughthe drain holes 168 onto the bearing plate 70 below. This gas fluid flowis indicated by arrow 188 (see FIG. 8 in particular). The gas fluid flowmoves radially inwardly across the upper surface of the bearing plate 70towards the central circular aperture in the housing insert 72. Thisflow across the bearing plate 70 tends to push separated oil dropletsacross the bearing plate 70 towards the bottom bearing unit 90, throughwhich said oil droplets pass. The rotating fan blades 140 of thecombined fan and turbine units 88 tend to lower the static pressure inthe turbine casing 178 in the region of the bottom bearing unit 90. Inturn, this assists in drawing oil droplets through the bottom bearingunit 90. However, the principal means by which oil droplets are drawnfrom through the bottom bearing unit 90 is provided by the deflectorwasher 139 which, in use, rotates with the turbine unit relative to thebearing plate 70 and pumps oil from the rotor housing 4, even if thepressure within the turbine housing is greater than that in the rotorhousing. The fan blades 140 then throw said droplets outwardly into theturbine casing 178 from where they may be returned to the engine crankcasing. Meanwhile, the gaseous fluid flowing across the bearing plate 70is drawn upwardly through the central aperture of the insert housing 72and exits the rotor housing 4 by means of the housing insert outlet 150and the rotor housing outlet 10.

It will also be appreciated with reference to the accompanying drawingsthat, as well as flowing through the drain holes 168, some of thecleaned gas flows to the outlet 150,10 via an alternative route betweenthe end plate 86 and the upper part of the ditch portion 154 (withoutflowing into the ditch 166). This alternative route is indicated byarrow 190.

It will be appreciated that the flow of oil through the bottom bearingunit 90 has a beneficial lubricating effect on the bearing unit. The topbearing unit 50 is similarly lubricated by an oil mist which naturallyoccurs in the turbine casing 178 and which is transported upwards to thetop bearing unit 50 through the longitudinal flow path 92 extendingthrough the rotary shaft 78.

Although the prior art separator 2 has proven to operate effectively,there are a number of problems associated with the separator which havebeen addressed with improvement found in the modified separatorsdescribed hereinafter. These problems can be considered in three broadcategories.

Firstly, the fluid pathways through the separator 2 give rise topressure loses which adversely affect the flow capacity of the separatorand, consequently, the size of engine with which the separator can beused. A first category of problem associated with the prior art ALFDEX™separator may therefore be regarded as relating to pressure losses inthe fluid flow pathways.

Secondly, the arrangement of the prior art separator is such that, undercertain conditions, cleaned gas can become contaminated before leavingthe separator. Accordingly, a second category of problem associated withthe prior art separator may be regarded as relating to an undesirableoil contamination of cleaned gas.

Thirdly, certain manufacturing techniques and construction featuresassociated with the prior art separator can lead to assemblydifficulties and/or reliability problems. As such, a third category ofproblem associated with the prior art separator may be regarded asrelating to the manufacture and reliability of the separator.

Each of these categories will now be discussed in greater detail.

Regarding the fluid flow pathways through the separator 2, there are anumber of locations at which comparatively high pressure losses areexperienced. Firstly, the inner corner 40 of the bend in theinlet/outlet nipples 22,28 is so sharp as to generate a separation offluid from the interior surface of the nipple in the region immediatelydownstream of said inner corner 40. This separation manifests itself asre-circulating fluid flow (or eddies), which in turn results inenergy/pressure losses. However, as described above in relation to FIG.4 of the accompanying drawings, providing a large radius on the innercorner is problematic when manufacturing the inlet/outlet nipple withinjection moulding or die casting techniques. As a result, the prior artseparator 2 experiences pressure losses at the nipples both on fluidentry to the rotor housing 4, and on exit from the valve unit housing12.

The inventors have also identified the six spokes 116 of the upper rotordisc 80 as a further cause of undesirable pressure losses. Specifically,it will be seen from FIGS. 5 and 6 in particular that the spokes 116each have a rectangular cross-section which presents a sharp uppertrailing edge to an incoming axial flow of vented gas when the upperrotor disc 80 is rotating in the direction of arrow 134 (see FIG. 5).The shape of the spokes 116, and in particular the sharp trailing edge192 of each spoke, has been found to give rise to fluid separation andundesirable pressure losses. The inventors have also found that theparticular configuration of the housing insert 72 gives rise toundesirable pressure losses. Specifically, during use of the separator2, cleaned gas flows downwardly over the frusto-conical portion 156 ofthe housing insert 72 with a rotary motion about the central axis 64 asindicated by arrow 194 in FIG. 12. This flow of cleaned gas flows overthe frusto-conical portion 156 after having flowed downwardly in aspiralling pattern along the inner surface of the cylindrical side wallof the rotor housing 4. It will be understood therefore that the cleanedgas enters the region between the frusto-conical portion 156 and theabove end plate 86 from all points along the circumferential perimeterof the housing insert 72 (rather than from entering said region at oneparticular location). The flow path across the frusto-conical portion156 therefore has a swirling pattern which can give rise to undesirablepressure/energy losses. Furthermore, the step 172 and walls 174,176 ofthe recess 170 provided in the frusto-conical portion 156 generatesfurther areas of fluid separation and associated undesirable pressurelosses.

With regard to the second category of problem relating to oilcontamination, the inventors have identified a number of features of theprior art separator 2 which increase the likelihood of cleaned airbecoming contaminated under certain conditions. Firstly, as previouslymentioned, the flow of cleaned gas downwardly through the rotor housing4 partly enters the ditch 166 and tends to draw separated oil dropletsthrough the drain holes 168. If the flow rate of cleaned air isinsufficiently high for the particular level of oil contamination beingtreated, then the oil droplets collecting in the ditch 166 can climb upthe ditch portion 154 of the housing insert 72 and then flow onto thefrusto-conical portion 156 of the housing insert 72 (see FIG. 10). Onceoil droplets enter the region between the frusto-conical portion 156 andthe end plate 86, the oil droplets inevitably exit the separator 2contaminating the cleaned gas. The climbing of oil droplets from theditch 166 can be a result of a low flow rate of cleaned gas which allowsan undesirably high quantity of oil to collect in the ditch 166. Thepresence of upwardly circulating cleaned gas within the ditch 166 mayalso tend to draw oil droplets upwards and onto the frusto-conicalportion 156 of the housing insert 72. However, a significant feature ofthe prior art separator 2 which allows oil droplets to climb upwardlyout of the ditch 166 is the tubular outlet portion 158 (see FIG. 12).Although drain holes 168 are located either side of the outlet portion158, it will be appreciated from FIG. 12 of the accompanying drawingsthat oil droplets within the ditch 166 follow a circular path along thebottom of the ditch 166 and if oil droplets do not flow through thedrain hole 168 immediately upstream of the outlet potion 158, then theoil droplets will tend to follow the path indicated by arrow 196 (seeFIG. 12) and flow upwardly over the outlet portion 158 and onto thefrusto-conical portion 156 of the housing insert 72.

The inventors have also found that separated oil droplets may flowupwardly through the central aperture of the housing insert 72 and ontothe frusto-conical portion 156 and thereby contaminate cleaned gas. Thisundesirable flow of separated oil tends to occur when the flow rate ofcleaned gas through the drain holes 168 and upwardly through the centralaperture of the housing insert 72 (as denoted by arrow 188 in FIG. 8) isrelatively high. It will be understood by those skilled in the art thatthe high flow rate of cleaned gas results in separated oil dropletsbeing carried upwards through the central aperture of the housing insert72 rather than allowing the separated oil droplets to be drawn downwardsthrough the bottom bearing unit 90 by the action of gravity and thedeflecting washer 139.

The inventors have also found that excessive oil can be introduced intothe separator disc stack 84 via the longitudinal flow path 92 throughthe rotary shaft 78, as denoted by the arrow 198 shown in FIG. 2. Duringordinary operating conditions, the jet of oil driving the turbine wheel136 impacts on said wheel and generates a mist of fine oil droplets.This mist of oil is transported upwards to the top bearing unit 50 andthen downwardly through the stack of separator discs 82. Ordinarily, thequantity of oil transported in this way is sufficient to lubricate thetop bearing unit 50 whilst being subsequently readily separated from theincoming flow of gas by the separator disc stack 84. However, in certaincircumstances, the quantity of oil transported through the rotary shaft78 can be so great as to result in oil overflowing the ditch 166 orotherwise flowing onto the frusto-conical portion 156 of the housinginsert 72 and subsequently into the cleaned gas outlet 10. This canoccur when, for example, the separator 2 is tilted and the lower end ofthe rotary shaft 78 is directly exposed to the surface of an oilreservoir held within the turbine casing 178.

Regarding the third category of problem relating to difficulties withmanufacture and reliability, the inventors have identified the followingissues with the prior art separator 2.

Firstly, with regard to manufacturing the separator 2, the inventorshave found that the use of threaded fasteners 32 to secure aninlet/outlet nipple to the rotor housing 4 and valve unit housing 12 canbe time consuming, and requires an O-ring seal 36.

The length of time taken to manufacture the prior art separator 2 isalso affected by the need for the top bearing unit 50 to be axiallyaligned with the bottom bearing unit 90 in such a way that both bearingunits 50,90 are rotatable about the same axis 64. Specifically, therotor housing 4 is made from a plastics material by means of aninjection moulding process and the inventors have found that there is atendency for the rotor housing 4 to warp during cooling. As aconsequence of this warping, the position of the first cylindrical wall60 of the rotor housing 4 (which laterally locates the top bearing unit50) tends to locate in a different lateral position relative to thelower end of the rotor housing 4 than was intended. As a result, thebearing plate 70 (and, accordingly, the bottom bearing unit 90) canbecome laterally offset from its intended position. This problem can bemitigated by allowing the rotor housing 4 to cool over a comparativelylong period following the injection moulding process. This long coolingperiod reduces the warping of the rotor housing 4, but increases themanufacturing time.

A further problem associated with the assembly of the separator 2relates to the interface between various components, such as thatbetween the rotor housing 4 and the valve unit housing 12. Morespecifically, if the separator 2 is to be provided with a differentvalve unit 14 to that originally intended (or indeed without a valveunit), then a different rotor housing 4 must also be used in order toensure the correct interface with the new valve unit (or other pipesystem where no valve unit is to be used). This can unduly increasecosts and assembly times. Furthermore, the asymmetry of the rotorhousing 4 (caused by the moulding profile provided on said housing 4 forinterfacing with the valve unit housing 12) tends to result in a warpingof said housing 4 during manufacture and this in turn tends to result inproblems during assembly (for example, problems relating to themisalignment of components).

It has also been identified by the inventors that the large O-ring seal160 provided on the housing insert 72 can fail. More specifically, theO-ring seal is required to seal against two mating large diametersurfaces, one surface being provided on the housing insert 72 and onesurface being provided on the cylindrical wall of the rotor housing 4.Both the rotor housing 4 and the housing insert 72 have relatively largemanufacturing tolerances which can result in the O-ring seal 160 notcorrectly sealing the two components. Furthermore, since the twocomponents are manufactured from a plastics material using injectionmoulding techniques, each moulding (and particularly the moulding of therotor housing 4) are subject to warping following the injection mouldingprocess. This can further result in the O-ring seal 160 failing tocorrectly seal the two components 4,72. It will be understood that, ifthe O-ring seal 160 fails, then separated oil will leak into the region200 between the outer cylindrical skirt portion 152 of the housinginsert 72 and the cylindrical wall of the rotor housing 4. Oil leakinginto this region 200 will ultimately pass into the outlet 150 of thehousing insert 72 and contaminate cleaned gas. If the O-ring seal 160fails in the locality of the outlet 150, then separated oil will tend toleak past the O-ring seal 160 and directly enter the outlet 150. Thissealing problem can increase the manufacturing time when: (i) action istaken to reduce the warping effect (by increasing the cooling timefollowing the injection moulding process), or (ii) leaking componentsare replaced following product testing.

In addition, a moulding burr located in the recess 159 receiving theO-ring seal 160 can result in the O-ring seal failing.

The inventors have also identified a reliability issue associated withthe arrangement for locating the separator discs 82 in a fixed angularorientation relative to the rotary shaft 78. As explained above inrelation to FIG. 7 of the accompanying drawings, the separator discs 82are prevented from rotating relative to the rotary shaft 78 by means ofsix splines (fixed to the rotary shaft 78) engaging with a hexagonalaperture in the hub 120 or each separator disc 82. However, vibrationsto which a separator is typically exposed during use (such as enginevibrations) can cause a wearing of the interface between the splines 122and the hexagonal aperture in the hub 120. This wear can result insignificant relative rotary movement between the separator discs 82 andthe rotary shafts 78. Indeed, the inventors have found that adjacentseparator discs 82 can rotate relatively to one another to such anextent that the caulks 100 become misaligned allowing the space betweenadjacent separator discs 82 to close. If this occurs with a significantnumber of discs 82, then the depth of the separator disc stack 84 canreduce to such an extent that the hub 98 of the end plate 86 is pressedby the compression spring 96 against the upper rotor disc hub 114. Itwill be understood that the end plate 86 is then no longer capable oftransmitting a compression force to the separator disc stack 84 and, asa consequence, individual separator discs 82 will be free to moveaxially up and down along the rotary shaft 78 (as well as rotaterelative to the rotary shaft 78). This movement is highly undesirableand significantly reduces the separating performance of the separatordisc stack 84.

A further reliability issue identified by the inventors relates tofretting corrosion at the interfaces between (i) the rotary shaft 78 andthe top/bottom bearing units 50,90; and (ii) the rotary shaft 78 and thefirst compression spring 96. It will be understood by those skilled inthe art that fretting corrosion occurs when relative movement betweencomponents is possible (for example, due to a relatively loose fitbetween said components). The rotary shaft 78 extends through the topand bottom bearing units 50,90 and the first compression spring 96 witha relatively loose fit. This allows an axial preload to be applied tothe top and bottom bearing units 50,90 by the first and secondcompression springs 96,130. Specifically, it will be understood from thedrawings that the first compression spring 96 applies an axial force tothe bottom bearing unit 90, and the second compression spring 130applies an axial force to the top bearing unit 130. The loose fit of therotary shaft 78 with the top/bottom bearing units 50,90 and the firstcompression spring 96 allows vibratory movements between the components.This, in turn, gives rise to fretting corrosion on said components. Therelative movements between the components can also allow an ingress ofhard particles between said components which can further accelerate wearand lead to reliability problems.

Improved separators developed by the inventors to address the aboveproblems will now be described with reference to FIGS. 13 to 41.

Those skilled in the art will immediately understand from theaccompanying drawings that the improved separators developed by theinventors have many components that are similar or identical to theprior art separator 2 in terms of the function they perform and theirgeneral configuration. Such components will be described hereinafter inthe context of the improved separators by using the same referencenumerals as has been used above in relation to the prior art separator2. For example, with reference to FIG. 13 of the accompanying drawings,a skilled person will understand that the improved separator 2′ shown inthis Figure comprises a generally cylindrical rotor housing 4′ whichcorresponds to the rotor housing 4 of the prior art separator 2 andperforms a similar function. Structural and functional differencesbetween such corresponding components will be evident to the skilledperson from the accompanying drawings, however these will, in general,be discussed in detail when the differences are of significance inaddressing problems with, and providing improvements over, the prior artseparator 2 or the process of manufacturing the prior art separator 2.

It will be understood by those skilled in the art that the improvedseparator 2′ comprises a generally cylindrically shaped rotor housing 4′and a number of internal components which function to separate oil fromvented gas directed into said rotor housing 4′. As described below, someof the internal components are located within the rotor housing 4′,whilst other internal components (for example, a combined fan andturbine unit) are located exteriorly of the rotor housing 4′ but arenevertheless located in another housing (for example, a turbine casing).

An upper end of the cylindrical housing 4′ is provided with anupstanding annular shoulder 6′, which defines a fluid inlet 8′ to theimproved separator 2′. Gas vented from a crank casing, and requiring theremoval of oil therefrom, enters the separator 2′ via the fluid inlet8′.

An aperture 10′ in a cylindrical wall 201 of the rotor housing 4′provides an outlet through which cleaned gas passes from the interior ofthe rotor housing 4′ into a separate housing 12′ of a valve unit 14′(see FIGS. 13, 14 and 15 in particular). The outlet aperture 10′ extendsthrough, and is therefore surrounded by, a cylindrical boss 202 whichitself extends from the outer surface of the rotor housing 4′.

The valve unit 14′ comprises a valve arrangement for controlling theflow of cleaned gas from the separator 2′. As for the above descriptionof the prior art separator 2, detail of the operation of the valve unit14′ will not be described herein. A skilled person will, however, befamiliar with the functional operation of a valve unit for use with theimproved separator.

As will be evident from FIGS. 13 and 14, and in particular from FIG. 15,the internal components of the valve unit 14′ are entirely enclosed in ahousing 12′ that is discrete from the rotor housing 4′. Morespecifically, the valve unit housing 12′ comprises first and secondparts 203,205 which mate with one another to form a sealed enclosedspace in which the internal components of the valve unit 14′ arearranged. With reference to FIG. 15, it will be seen that an upper endof the first part 203 of the valve unit housing 12′ is provided with aboss 207 through which a conventional screw threaded fastening 16′extends for screw threaded engagement with a further boss 209 on therotor housing 4′.

It will also be seen from FIG. 15 that a lower end of the first part 203of the valve unit housing 12′ is provided with a generally cylindricalportion 211 which extends away from the valve unit housing 12′ and intothe interior of the rotor housing 4′ via the outlet aperture 10′ in therotor housing 4′. An O-ring seal 213 is located on an exterior surfaceof the cylindrical portion 211 and abuts against a shoulder (defined onsaid surface) which faces the interior of the rotor housing 4′ in theassembled separator 2′. The shoulder thereby prevents an undesirablemovement of the O-ring seal 213 along the cylindrical portion 211 assaid portion 211 is pushed through the outlet aperture 10′ duringassembly and the O-ring seal 213 engages with said aperture 10′. Morespecifically, the O-ring seal 213 sealingly engages with the interiorcylindrical surface of the boss 202 surrounding the outlet aperture 10′.

Whilst the O-ring seal 213 is provided towards the root end of thecylindrical portion 211 (i.e. the end of the cylindrical portionadjacent the remainder of the valve unit housing), a second O-ring seal215 is provided on the exterior surface of a free end of the cylindricalportion 211 (distal to the root end). As in the case of the first O-ringseal 213, the second O-ring seal 215 abuts against a shoulder facing theinterior of the rotor housing 4′ so as to prevent an undesirablemovement of the second O-ring seal 215 as said seal is pressed into afinal use position in the assembled separator 2′. More specifically, itwill be understood from FIG. 15 that, in the assembled separator 2′, thesecond O-ring seal 215 sealingly engages with the outlet 150′ of ahousing insert 72′.

It will also be understood by the skilled person that the first O-ringseal 213 prevents cleaned gas and/or oil droplets from leaking betweenthe rotor housing 4′ and the valve unit housing 12′ and from therebyundesirably leaking from the separator 2′ into the environment. It willbe yet further understood by the skilled person that the second O-ringseal 215 prevents oil droplets from leaking into the outlet 150′ of thehousing insert 72′ and thereby contaminating cleaned gas exiting therotor housing 4′ via the cylindrical portion 211. The small externaldiameter of the cylindrical portion 211 and of the first and secondO-ring seals 213,215 (as compared with the large diameter O-ring seal160 of the prior art separator 2) allows the use of comparatively smallmanufacturing tolerances which ensures a low failure rate in respect ofthe two O-ring seals 213,215. In this regard, it will be appreciated,for example, that the extent of warping in the relatively small diametercylindrical portion 211 will be less than in the relatively largediameter rotor housing 4 of the prior art separator 2.

The lower end of the first part 203 of the valve unit housing 12′ isprovided with a second boss 207 located to one side of the cylindricalportion 211. As in the case of the first boss 207 provided on the upperend of the first part 203, the second boss 207 on the lower end of thefirst part 203 receives a conventional screw threaded fastening 16′ forscrew threaded engagement with a second boss 209 provided on a lower endof the rotor housing 4′ (see FIG. 18 in respect of said second bosses207,209).

As a consequence of the valve unit housing 12′ being a discrete housingto the rotor housing 4′ and being geometrically independent thereof(other than for the mating of the cylindrical portion 211 with theoutlet aperture 10′ and the interfacing of the upper and lower pairs ofbosses 207,209), the rotor housing 4′ of the improved separator 2′ hasan overall shape which approximates that of a cylinder more closely thanthe rotor housing 4 of the prior art separator 2. In this regard, it isnoted that the prior art rotor housing 4 comprises a relatively complexand bulky moulding profile on one side which serves to form part of theprior art valve unit housing 12 (rather than merely a mating interfacetherewith). However, with reference to FIG. 15, it will be seen that therotor housing 4′ of the improved separator 2′ does not comprise theaforementioned complex and bulky moulding profile.

As a consequence of the rotor housing 4′ having a shape approximatingthat of the cylinder, the housing 4′ may be manufactured using injectionmoulding techniques with a reduced amount of warping during the coolingprocess as compared with the housing 4 of the prior art separator 2.This allows for a more ready axial alignment of top and bottom bearingunits 50′,90′. Furthermore, it will be appreciated that the rotorhousing 4′ shown in the accompanying drawings may be coupled withalternative valve units to the valve unit 14′ shown in the accompanyingdrawings provided the alternative valve units have a cylindrical portion211 suitable for mating with the outlet aperture 10′ of the rotorhousing 4′ and bosses 207 suitable for mating with the bosses 209 of therotor housing 4′ (as in the case of the valve unit housing 12′ shown inFIG. 15). For example, if an alternative valve unit has a housing with acylindrical portion and two bosses identical to the cylindrical portion211 and bosses 207 shown in FIG. 15, and with the same relativepositioning as shown in FIG. 15, then the alternative housing may beconsiderably larger than the valve unit housing 12′ shown in FIG. 15 andhouse an entirely different internal valve arrangement to that of thevalve unit 14′ shown in the accompanying drawings. This allows for amodular construction of a separator 2′ with an increased commonality ofparts between different arrangements of separator.

With reference to FIG. 15, it will be seen that the housing 12′ of thevalve unit 14′ is provided with an upstanding annular shoulder 18′ thatdefines a fluid outlet through which cleaned gas passes from theseparator 2′. The annular shoulder 18′ provided on the valve unithousing 12′ is substantially identical to the annular shoulder 6′provided on the rotor housing 4′. Due to their similarity, the inlet andoutlet shoulders 6,18 may interchangeably receive inlet/outlet nippleshaving the same interface profile. Identical inlet/outlet nipples 22′having a 90° bend are shown in FIG. 13. The inlet nipple 22′ is shown,in cross-section, mated with the shoulder 6′ of the rotor housing 4′,and is further shown separated from said shoulder 6′ in FIG. 17.

As will be most clearly seen from the cross-sectional side view of FIG.16, the internal surface 216 of the nipple 22′ combines with a curvedsurface of the shoulder 6′ to define a fluid flow path having a 90° bendand, significantly, with a radius both on the outer and inner corners.As a result, the tendency for fluid to separate from the inner corner ofthe bend is much reduced as compared with the fluid flow over the sharpcorner 40 of the prior art arrangement. In turn, pressure losses arealso reduced.

The interface between the inlet/outlet nipples 22′ and the respectivehousing shoulders 6′,18′ will now be described in more detail withreference to the rotor housing shoulder 6′ (which is identical to theshoulder 18′ of the valve unit housing 12′).

As shown in FIGS. 16 and 17, the upstanding shoulder 6′ of the rotorhousing 4′ is provided as an annular boss having a generally cylindricalwall 217 centred on a longitudinal axis coincident with a central axis64′ of the rotor housing 4′. A free end of the cylindrical wall 217(distal to the remainder of the rotor housing 4′) is provided with acircumferential lip 219 forming a curved surface 221 extending inwardlyinto an aperture formed by the shoulder 6′. In cross-section (see FIG.16), the curved surface 221 has a part-circular shape and extendsthrough an arc 223 of approximately 110°. The part-circular surface 221is oriented so that a radial 225 of said surface 221 extends parallelwith the longitudinal axis of the cylindrical wall 217. In theparticular arrangement shown in FIG. 16, the arc 223, through which thepart-circular surface 221 sweeps, terminates at the aforementionedradial 225. It will also be understood from the cross-sectional sideview of FIG. 16 that an exterior cylindrical surface 227 of the shoulder6′ is coincident with said radial 225 and intersects with thepart-circular surface 221 to form an upper edge 229 of the shoulder 6′.

Again, with reference to FIG. 16 in particular, that the nipple 22′ willbe understood to be provided with a profile for mating with the shoulder6′ such that the internal surface 216 of the nipple 22′ combines withthe part-circular surface 221 of the shoulder 6′ to provide a smoothsurface absent of ridges, upstream/downstream facing shoulders,discontinuities, and/or any other features which generate pressurelosses. More specifically, the geometry of the nipple 22′ is such thatthe transition from the interior surface 216 of the nipple 22′ to thepart-circular surface 221 of the shoulder 6′ does not present a flow offluid over the combined surface (in either direction through the nipple22′) with an obstruction or other pressure loss generating feature.Given the symmetry of the shoulder 6′, this remains the case regardlessof the angular or polar positioning of the nipple 22′ relative to thehousing 4′.

The smooth transition between the interior surface of the nipple 22′ andthe part-circular surface 221 is achieved in the arrangement of theimproved separator 2′ by configuring the internal surface of the nipple22′ so that, at each point where the internal nipple surface 216 meetsthe part-circular surface 221, the internal nipple surface 216 isoriented at a tangent to the part-circular surface 221. Accordingly,with regard to the inner corner of the bend formed by thenipple/shoulder combination, the internal nipple surface 216 meets withthe part-circular surface 221 at the aforementioned edge 229 of theshoulder 6′ and, at this meeting point, is oriented perpendicularly tothe aforementioned radial 225 (i.e. tangentially to the part-circularsurface 221). The point at which the internal nipple surface 216 meetsthe part-circular surface 221 of the shoulder 6′ moves progressivelyradially inwards over the part-circular surface 221 as one progressescircumferentially around the shoulder 6′ to the outer corner of the bendformed by the nipple/shoulder combination. The internal nipple surface216 can be seen in FIG. 16 meeting with the part-circular surface 221 atan edge 231 of the internal nipple surface 216.

In practice, due to the limitations of injection moulding techniques andthe cost constraints associated with high tolerances, the transitionbetween the part-circular surface 221 and the internal nipple surface216 will not necessarily be entirely free of discontinuities or otherpressure loss generating features. In particular, there can be a gapbetween the edge 231 of the nipple 22′ and the part-circular surface 221of the shoulder 6′ . This gap can be reduced in practice bymanufacturing one or both of the nipple 22′ and part-circular surface221 from steel (or other metallic material) with die casting techniques.

The nipple 22′ is further provided with a generally cylindrical shoulderin the form of a cylindrical wall 233 which has internal and externaldiameters equal to that of the cylindrical wall 217 of the housingshoulder 6′. The cylindrical wall 233 of the nipple 22′ matesconcentrically with the cylindrical wall 217 of the housing shoulder 6′when the nipple 22′ is located on said shoulder 6′. A curved wall 235extends radially outwardly from the aforementioned internal nipplesurface edge 231 to an upper edge of the nipple cylindrical wall 233. Incross-section, the curved wall 235 is part-circular in shape andconfigured to be concentric with, and to abut, the part-circular surface221 of the housing shoulder 6′.

Two fins 237 are located on the exterior of the nipple 22′ and extendfrom the curved wall 235 so as to provide said wall 235 with additionalrigidity and to prevent or reduce a flexing of the nipple 22′ betweensaid wall 235 and the remainder of the nipple 22′ (see FIG. 13).

As in the prior art separator 2, the nipple 22′ of the improvedseparator 2′ is manufactured using conventional injection moulding ordie-casting techniques with the consequence that a sharp inner corner239 is formed (see FIG. 34). This corner 239 may be considered analogousto the inner corner 40 of the prior art nipple 22. However, it will beunderstood that the presence of the part-circular surface 221 of thehousing shoulder 6′ in combination with the improved nipple 22′ ensuresa radius is provided to the inner part of the flow path bend at thehousing 4′. As alluded to above, this is irrespective of the angularorientation of the nipple 22′ relative to the housing 4′. Fluidseparation from the inner surface of the bend is thereby reduced oravoided, and pressure losses in this part of the flow path are similarlyreduced or avoided.

Finally, with regard to the geometry of the nipple 22′, a second end ofsaid nipple (distal to the end provided with the housing interfaceprofile) is provided with teeth or serrations 38′ on an exterior surfacethereof for gripping a hose which, in use, is located over the nipplesecond end.

It is again emphasised that the rotary housing shoulder 6′ is identicalto the shoulder 18′ on the valve unit housing 12′ and that an outletnipple 22′ is connected to this second housing shoulder 18′ in the sameway as described above in relation to the rotor housing shoulder 6′.

It will be understood from the above that the nipple 22′ may be rotatedunimpeded whilst positioned on and in abutment with the shoulder 6′ asshown in FIG. 16. As such, the nipple 22′ may be spun welded to theshoulder 6′ so as to fixedly secure the nipple 22′ to the housing in arequired angular orientation. It will be appreciated by those skilled inthe art that this method of securing the nipple 22′ does not require theuse of threaded fasteners as in the prior art separator 2. It will alsobe understood that this spin welding technique allows the nipple 22′ tobe secured in any angular orientation relative to the housing 4′ andprovides a full circumferential (or closed loop) seal without the needof an O-ring seal. Specifically, heat produced by friction forces actingbetween abutting surfaces of the housing 4′ (i.e. the shoulder 6′) andthe nipple 22′ during relative rotation of said surfaces results in saidsurfaces melting. Rotation is then stopped and said surfaces solidify,thereby bonding to one another.

Whilst the above spin welding is an effective method of bonding thematerial of the nipple 22′ to that of the housing 4′; other methods ofbonding said materials may be used (for example, adhesive bonding,ultrasonic welding or vibration welding).

The aforementioned internal components will now be described in greaterdetail with particular reference to FIG. 34.

Firstly, a top bearing unit 50′ is secured to an inner surface of therotor housing 4′ immediately downstream of the fluid inlet 8′. The topbearing unit 50′ is identical to the top bearing unit 50 of the priorart separator 2 and, as such, comprises caged bearings 52′ trappedbetween an upper steel cap member 54′ and a lower bearings seat member56′ of a plastics material. The top bearing unit 50′ (and also a bottombearing unit 90′) comprise roller bearings (as in the prior artseparator 2), but may alternatively comprise slide or friction bearings.

More specifically, the bearings seat member 56′ has a circular shape anda downwardly projecting cylindrical wall 58′ (encasing a lower part ofthe cap member 54′) which, in the assembled separator 2′, locates within(but without abutting laterally against) a cylindrical wall 60′ of therotor housing 4′. The cylindrical wall 60′ extends downwardly from anupper internal surface of the rotor housing 4′. A circular ridge 238also extends downwardly from an upper internal surface of the rotorhousing 4′ and is positioned radially inwardly of the first cylindricalwall 60′. The cylindrical wall 60′, circular ridge 238 andaforementioned shoulder 6′ of the rotor housing 4′ are positionedconcentrically with one another and are centred on the central axis 64′of the rotor housing 4′.

As will be described in greater detail below (with reference to FIGS. 37to 41), the top bearing unit 50′ is secured to the upper internalsurface of the rotor housing 4′ by means of a spin welding technique.Specifically, the lower bearings seat member 56′ is welded to the ridge238. Threaded fasteners are not used to secure the top bearing unit 50′to the roto housing 4′, as in the prior art separator 2. The arrangementis such that the rotary axis of the top bearing unit 50′ is coincidentwith the central axis 64′ of the rotor housing 4′.

Three part-circular slots 66′ (only two of which are shown in FIG. 34)are provided in the top bearing unit 50′ so as to allow a flow of inletfluid therepast (as shown by arrows 68′). The upper cap member 54′deflects inlet fluid from the caged bearings 52′. As in the prior artseparator 2, the underside of the uppermost part of the cap member 54′also deflects (into the caged bearings 52′) a lubricating oil mist whichtravels upwardly through a rotor shaft during use.

The remaining internal components of the separator 2′ are assembledseparately to the rotor housing 4′ and are then removably located, inpart, within the housing 4′ as a unitary assembly. As for the prior artseparator 2, this unitary assembly may be considered as comprising afirst group of components which, in use, remains stationary relative tothe rotor housing 4′, and a second group of components which, in use,rotates about the central axis 64′ relative to both the rotor housing 4′(and the valve unit housing 12′) and the first group of components.

The first group of components comprises an annular-shaped bearing plate70′ and a dish-shaped housing member/insert 72′. As in the prior artseparator 2, the housing insert 72′ and the bearing plate 70′ functionin combination with one another to segregate separated oil from cleanedgas prior to the separated oil and cleaned gas exiting the rotor housing4′. The bearing plate 70′ is made of steel and the housing insert 72′ ismade of a plastics material. The bearing plate 70′ and housing insert72′ are secured to one another by means of three screw threadedfasteners 74′ (see FIG. 29) which threadedly engage bosses 76′projecting downwardly from an underside of the housing insert 72′. Thebearing plate 70′ closes the open end of the rotor housing 4′ to providean enclosed inner space of the housing 4′ in which several of the secondgroup of components are located. In this respect, the rotor housing 4′may be regarded as a first housing part defining an inner space forreceiving components for separating substances (for example, oil andgas) and directing the separated substances to different outlets fromsaid inner space. The bearing plate 70′ may be considered as a secondhousing part defining said inner space with the first housing part.

The first group of components will be discussed in greater detail laterin this description.

The second group of components form a rotor assembly and comprises arotary shaft 78′, an upper rotor disc 80′, a plurality of individualseparator discs 82′ which together form a stack 84′ of separator discs82′, a fan disc 240, an end member/plate 86′, a splash guard disc 242,and a combined fan and turbine unit 88′. The rotary shaft 78′ is made ofa metallic material, whilst the remainder of the aforementionedcomponents of the second group are of a plastics material andmanufactured with injection moulding techniques. The aforementionedcomponents of the second group are secured to one another in such a wayas to prevent or at least limit their rotation relative to one another.Helical compression springs (of a metallic material) are also providedin the second group of components, as will be described in greaterdetail below. The second group of components is rotatably mounted to thefirst group of components by means of a bottom bearing unit 90′ and, inthe assembled separator 2′, is rotatably mounted to the rotor housing 4′by means of the top bearing unit 50′.

The rotor assembly formed by the second group of components will now bedescribed in more detail.

The rotary shaft 78′ has an annular cross-section so as to provide alongitudinally extending fluid flow path 92′ along its entire length. Inuse of the separator 2′, this flow path 92′ allows an oil mist to betransported from a turbine casing upwardly through the rotary shaft andinto the top bearing unit 50′ so as to lubricate the bearings of saidunit 50′. The exterior of the rotary shaft 78′ is provided with a numberof recesses and shoulders which assist in retaining components in thecorrect axial position on the rotary shaft 78′ .

Each of the upper rotor disc 80′, separator discs 82′, fan disc 240, andend plate 86′ has a frusto-conical part (defining upper and lowerfrusto-conical surfaces) connected to a central hub element which, inuse, is located about the rotary shaft 78′.

In the case of the upper rotor disc 80′, separator discs 82′ and endplate 86′, the frusto-conical part is connected to the associatedcentral hub element with a plurality of spoke members extending radiallyinwardly therefrom. These spoke members have open spaces between them toallow for a flow of fluid axially therethrough along the rotary shaft78′ .

In the case of the fan disc 240, the frusto-conical part 290 isconnected to the associated central hub element 292 by means of a secondfrusto-conical part 294. This second frusto-conical part 294 iscontinuous so as to provide a barrier to fluid and thereby prevent anaxial flow of fluid along the rotary shaft 78′ either upwardly past thefan disc 240 or downwardly past the fan disc 240.

The frusto-conical shape of the second frusto-conical part 294 has alarger included angle than that of the other frusto-conical parts of theimproved separator 2′. In other words, opposite sides of the secondfrusto-conical part 294 diverge/converge more rapidly than in the caseof the first frusto-conical part 290 of the fan disc 240 or of thefrusto-conical parts of the upper rotor disc 80′, separator discs 82′and end plate 86′ (and, indeed, the frusto-conical shaped segregatingroof member 268 of the housing insert 72′), all of which have the sameincluded angle. The central hub element 292 is a cylindrical wallupstanding from the second frusto-conical part 294 (see FIGS. 26 and 33in particular). Longitudinally extending slots 296 (only one of which isshown in FIG. 26) are provided through the full thickness of thecylindrical wall of the fan hub element 292 for receiving a spline 254extending radially from the rotary shaft 78′. In this way, rotation ofthe fan disc 240 relative to the rotary shaft 78′ IS prevented.

The underside of the first frusto-conical part 290 of the fan disc 240is provided with a plurality of caulk members 298 spaced equidistantabout the central axis of the fan disc 240. Each caulk member 298 isprovided as a straight ridge projecting downwardly from the underside ofthe first frusto-conical part 290 and extends in a radial direction froma radially innermost edge of the first frusto-conical part 290 to aradially outermost edge of the first frusto-conical part 290. In theassembled separator 2, the caulk members 298 abut the upper surface ofthe frusto-conical part of the end plate 86′ and thereby ensure aspacing between the fan disc 240 and the end plate 86′ through whichfluid may pass (as indicated by arrow 188′ in FIG. 34). During use ofthe separator 2′, rotation of the caulk members 298 imparts a rotarymotion onto fluid between the fan disc 240 and the end plate 86′. As aconsequence, said fluid is moved outwards towards the cylindrical wall201 of the rotor housing 4′. Oil droplets (and/or, indeed, other liquidor particulate contaminants carried by the gas flow) are effectivelythrown against the cylindrical wall 201 of the rotary housing 4′ andflow (or fall) downwardly onto the bearing plate 70′. The gaseous fluidejected from the space between the fan disc 240 and end plate 86′ eitheralso flows downwardly onto the bearing plate 70′ or directly exits therotor housing 4′ as will be explained in greater detail below.

With regard to the end plate 86′, a radially innermost circular edge ofthe frustoconical part 108′ is connected to a central hub element 98′ bymeans of a plurality of spoke members 110′ (see FIG. 18). However, acylindrically shaped wall 300 also extends downwardly from said radiallyinnermost edge of the frusto-conical part 108′. In the assembledseparator 2′, the cylindrical wall 300 is centred on the central axis64′ and extends sufficiently downwards along the rotary shaft 78′ as toextend through the central aperture provided in the insert housing 72′.Although said wall 300 has a generally cylindrical shape, the innersurface 302 of said wall 300 defines a frusto-conical shape such thatthe internal diameter of the cylindrical wall 300 reduces in an upwardsdirection in the assembled separator 2′. The external cylindricalsurface of the wall 300 has a diameter substantially the same as thecentral aperture of the housing insert 72′ and, in the assembledseparator 2′, locates in said aperture with minimal spacing between thewall 300 and the insert housing 72′. This close fit, whilst allowingrelative rotation between the end plate 86′ and the insert housing 72′,assists in reducing the quantity of separated oil which may flow betweensaid wall 300 and the central aperture of the insert housing 72′ so asto contaminate cleaned gas. Furthermore, the internal frusto-conicalsurface 302 of said wall 300 functions to resist a passage of oildroplets flowing upwards into the space between the fan disc 240 and theend plate 86′. It will be understood by those skilled in the art thatoil droplets contacting the frusto-conical surface of the wall 300 willbe subjected to a rotary motion and, due to the frusto-conical shape ofsaid surface, a downwardly acting force.

The splash guard disc 242 includes a planar annular disc 304 which isconnected, by means of six spoke members 306 extending radially inwardlytherefrom, to a central hub element 308 which, in the assembledseparator 2′, is located about the rotary shaft 78′ (see FIG. 28 inparticular). The diameter of the central aperture defined by the planarannular disc 304 is substantially equal to the inner diameter of thelower end of the cylindrical wall 300 of the end plate 86′. A flow offluid passing through the splash guard disc 242 into the region betweenthe fan disc 240 and the end plate 86′ is not therefore presented with asignificant pressure loss generating feature at the junction between thesplash guard disc 242 and the end plate 86′. It will be understood thatthe annular disc 304 provides a flange member extending radially fromthe lower end of said cylindrical wall 300 and, in use, functions tocover any spacing between the exterior surface of said cylindrical wall300 and that part of the housing insert 72′ defining the centralaperture through which said wall 300 extends. In this way, the planarannular disc 304 reduces the likelihood of separated oil dropletssplashing or otherwise moving upwardly from the bearing plate 70′ andthrough the central aperture of the insert housing 72′ so as contaminatecleaned gas.

It will further be appreciated that said region between the fan disc 240and the end plate 86′ defines a flow path 616 for fluid to pass throughfrom an inlet 618 (defined by the splash guard disc 242) to an outlet620 (defined by the radially outer perimeter edges of the fan disc 240and the end plate 86′), as shown in FIG. 34.

The hub element 308 of the splash guard disc 242 is provided as acylinder with an upper end thereof closed with a planar wall arrangedperpendicular to the longitudinal axis of said cylinder (and, in theassembled separator 2′, to the central axis 64′). The internal diameterof said cylinder is greater than the external diameter of the rotaryshaft 78′ and the planar wall is provided with a central aperturethrough which said shaft 78′ passes in the assembled separator 2′. Thearrangement is such that, in the assembled separator 2′, the rotaryshaft 78′ and the cylinder of the hub element 308 define an annularspace therebetween which receives a helical compression spring 96′ forpressing the splash guard disc 242 into abutment with the end plate 86′,which, in turn, compresses the fan disc 240 and disc stack 84′ againstthe upper rotor disc 80′.

It will be understood by those skilled in the art that the splash guarddisc 242 is manufactured separately from the end plate 86′ so as toallow the cylindrical wall 300 of the end plate 86′ to be locatedthrough the central aperture as the insert housing 72′. This would notbe possible if the splash guard disc 242 was integral with the end plate86′ because the outer diameter of the annular disc 304 is greater thanthe diameter of the central aperture in the housing insert 72′ .

As alluded to above, the frusto-conical geometry of the upper rotor disc80′, fan disc 240 (with respect to the first frusto-conical partthereof) and end plate 86′ is substantially identical to that of theseparator discs 82′. This allows the upper rotor disc 80′, fan disc 240and end plate 86′ to be stacked with the separator discs 82′, whereinthe upper rotor disc 80′ is located at the top of the separator discstack 84′ and the end plate 86′ is located at the bottom of theseparator disc stack 84′. The fan disc 240 is located between the endplate 86′ and the separator disc 82′ lowermost in (i.e. at the bottomof) the separator disc stack 84′.

Furthermore, whilst the separator discs 82′ will be understood by theskilled person to be comparatively thin so as to allow a large number ofdiscs to be provided in a relatively short stack 84′, the upper rotordisc 80′ and end plate 86′ are considerably thicker than the separatordiscs 82′ so as to provide rigidity at either end of the disc stack 84′and thereby allow a compressive axial force to be uniformly applied tothe frusto-conical parts of the separator discs 82′ by means of theupper disc 80′ and end plate 86′. It will be understood that thecompressive force is generated by said helical compression spring 96′which presses upwardly on the underside of a hub 308 of the splash guarddisc 242. In turn, the hub 308 of the splash guide disc 242 pressesupwardly on the underside of the abutting hub 98′ of the end plate 86′.

Regarding the compression of the disc stack 84′ between the upper disc80′ and the end plate 86′, it will be understood by the skilled personthat, as in the prior art separator 2, adjacent separator discs 82′within the stack 84′ must remain spaced from one another in order toallow a flow of fluid through the improved separator 2′. This spacing ofthe separator discs 82′ is provided in the improved separator 2′ bymeans of a plurality of spacers 246. Each spacer 246 is a small dotlocated on, and standing proud of, the upper surface 102′ of thefrusto-conical part 124′ of each separator disc 82′ (see FIG. 20).

The separator disc 82′ lowermost in the stack 84′ may, optionally, alsobe spaced from the fan disc 240 so as to allow a flow of fluidtherebetween. If such spacing is required, then suitable spacers areused. Ideally, the upper surface of the first frustoconical part of thefan disc 240 (which locates below the frusto-conical parts of the discstack 84′ and is connect to the fan disc hub by means of the secondfrusto-conical part of the fan disc 240) is provided with spacers 246 inthe same way as the frustoconical part of each separator discs 82′.

Each of said spacers 246 has a circular shape, although other shapes maybe used (for example, an oval shape may be used). Any alternative shapesfor the spacers 246 preferably have curved edges so as to reduce fluidpressure losses in fluid flowing past the spacers.

A first group of spacers 246 are arranged in a circle concentric withand adjacent to an inner circular edge 104′ of said upper surface 102′.Each spacer 246 in this first group is located adjacent to that part ofthe inner circular edge 104′ where a spoke of the disc 82′ joins thefrusto-conical part of the disc 82′. A second group of spacers 246 arearranged in a circle concentric with and adjacent to an outer circularedge 106′ of said upper surface 102′. A third group of spacers 246 arearranged in a circle concentric with and approximately midway betweenthe inner and outer circular edges 104′ ,106′ of the frusto-conical partof the disc 82′.

As will be explained in greater detail below, each separator disc 82′(and, indeed, the fan disc 240) is locatable on the rotary shaft 78′ inone of only three possible angular positions relative to the rotaryshaft 78′, and the positioning of the spacers 246 on said upper surface102′ is such that the spacers 246 of adjacent discs 82′ must align withone another when the discs 82′ are arranged in any of these threepositions. In other words, when the separator discs 82′ are pushedaxially onto the rotary shaft 78′ and into abutment with one another toform the aforementioned stack 84′, it is inevitable that (i) each spacer246 of a particular disc 82′ locates directly above a spacer 246 of anadjacent disc 82′ located below said particular disc 82′ in the stack84′, and that (ii) each spacer 246 of a particular disc 82′ locatesdirectly below a spacer 246 of an adjacent disc 82′ located above saidparticular disc 82′ in the stack 84′. As a result, the compression forceapplied to the disc stack 84′ by the end plate 86′ is transmittedthrough the stack 84′ by means of the aligned spacers 246 without thespacing between adjacent separator discs 82 closing. This ensures fluidremains able to flow between the separator discs 82′.

It will be appreciated from the drawings that the spacers 246 have asmall radial dimension, as well as a small circumferential dimension,relative to the size (diameter) of the associated separator discs. Thisallows fluid to flow relatively unimpeded by the spacers in acircumferential direction across said disc upper surface 102′, as wellas in a radial direction across said surface 102′. This ensures pressurelosses in fluid flow between adjacent discs 82′ are minimised.

The upper rotor disc 80′ and rotary shaft 78′ is shown in isolation fromthe other components of the separator 2′ in FIGS. 21 and 23 of theaccompanying drawings. A hub 114′ of upper rotor disc 80′ is moulded tothe exterior surface of the rotary shaft 78′ and is thereby bonded tosaid shaft 78′. This bonding prevents relative rotation between the hub114′ and the rotary shaft 78′.

The hub 114′ of the upper rotor disc 80′ extends axially upwardly alongthe rotary shaft 78′ and terminates at the upper end of said shaft 78′.The upper portion of the rotary shaft 78′, about which a second helicalcompression spring 130′ locates, is thereby provided with a coating (asleeve) of a plastics material (preferably, a thermoplastics material).This coating protects the spring 130′ and, in particular, the shaft 78′,from fretting corrosion. The first and second groups of internalcomponents of an alternative embodiment to the first embodiment 2′ isshown in FIG. 19. The alternative separator is the same as the firstembodiment other than in that the upper end portion of the rotary shaft78′ is absent of the plastics coating adjacent the second helical spring130′.

The hub 114′ of the upper rotor disc 80′ also extends axially downwardlyalong the rotary shaft 78′ and terminates at a point just above thebottom bearing unit 90′. The bottom bearing unit 90′ thereby contacts ametallic end of the rotary shaft 78′ in the assembled separator 2′. Morespecifically, the hub 114′ extends along the full depth of the separatordisc stack 84′ and thereby separates the hub 120′ of each separator disc82′ from the rotary shaft 78′. It will also be understood that the hub114′ also provides the rotary shaft 78′ with a coating (a sleeve) of aplastics material (preferably, a thermoplastics material) in the regionof the first helical compression spring 96′. Again, this coatingprotects the spring 96′ and, in particular, the shaft 78′, from frettingcorrosion.

The frusto-conical part 112′ of the upper rotor disc 80′ is connected tothe hub 114′ by twelve radially extending spoke members 116′. Each spokemember 116′ has a rectangular-shaped cross-section, an upper (minor)side 310 of which adjoins the radially innermost circular edge 312 ofsaid frusto-conical part 112′. Each spoke member 116′ extends axiallydownwards from said edge 312. This arrangement is such that, when theupper rotor discs 80′ rotates during use of the separator 2′, each spokemember 116′ functions as a fan blade and imparts a motion on adjacentfluid. As will be understood by those skilled in the art, the motionimparted onto the fluid by each spoke member 116′ results in the fluidflowing tangentially from the circular path of the spoke members 116′and being effectively thrown outwards beneath the frusto-conical part112′ and through the disc stack 84′ towards the cylindrical wall of therotor housing 4′. The functioning of the spoke members 116′ as fanblades results in the rotation of the upper rotary disc 80′ drawing gasinto the rotor housing 4′ through the fluid inlet 8′ (as denoted byarrow 68′ in FIG. 34) and through the spaces 600 between the spokemembers 116′, whereby said spaces 600 represent an inlet to the rotorassembly.

The fluid entering the rotor housing 4′ passes through threepart-circular slots 66′ in the top bearing unit 50′. The spoke members116′ of the upper rotor disc 80′ are located immediately below the threepart-circular slots 66′ in the assembled separator 2′. With particularreference to FIG. 34 of the accompanying drawings, it will be seen thatthe radial dimension of the part-circular slots 66′ is less than theradial dimension (i.e. length) of the spoke members 116′ with the resultthat a large proportion of the incoming fluid initially impacts onlythat length of spoke member 116′ located directly beneath thepart-circular slots 66′. This length of each spoke element 116′ isprovided with a curved fluid guide vane 314 extending upwardly from theupper side (or leading edge) 310 thereof. The purpose of each guide vane314 is to reduce or eliminate pressure losses associated with aseparation of inlet fluid from the spoke members 116′. This is achievedby presenting the substantially axial flow of inlet fluid into the rotorhousing 4′ with a guide vane having an aerodynamically shapedcross-section and a cord oriented to have a substantially zero angle ofattack with the incoming flow of fluid (or another angle of attack whichdoes not result in a separation of fluid from the guide vane 314).

A view of a cross-section through a length of a spoke member 116′provided with a guide vane 314 is shown in FIG. 22. The surface of theguide vane 314 functions to guide fluid, which is approaching theleading edge 310 of a spoke element 116′, into alignment with the spokeelement 116′. A cord 316 associated with the leading edge 318 of theguide vane 314 is oriented to have a substantially zero angle of attackwith the fluid flowing over said guide vane 314. The direction of thisfluid relative to the guide vane 314 is denoted by arrow 320 and, asindicated in FIG. 22, will be understood to be a function of the axialvelocity of (i) inlet fluid flow (Q/A, wherein Q is volumetric fluidflow rate through the inlet; and A is the cross-sectional area of theinlet flow path), and (ii) the tangential velocity of the guide vane 314(ω.r wherein the ω is angular velocity of the upper rotor disc; and r isthe radial distance of the guide vane from the centre of rotation).Since the direction 320 of the fluid flow relative to the guide vane 314depends on the radial position r along a guide vane 314, the cord 316may be oriented at an angle which varies with radial position. In otherwords, the fluid guide vane 314 may be provided with a twist so as toensure a correct alignment of the guide vane 314 with the incoming fluidflow at all radial positions along the guide vane 314. Morespecifically, the acute angle 322 between the cord 316 and a verticaldatum line 324 (parallel with the central axis 64′ in the assembledseparator 2′) may progressively increase from an inner most radialposition towards an outer most radial position along a spoke member116′.

It will be understood by the skilled person that, during use of theimproved separator 2′, incoming air flows axially downwardly through thethree part-circular slots 66′ and impacts on the guide vanes 314 whichare located a short distance below said slots 66′ and which rotate in acircular path about the central axis 64′. Since the cord 316 of theleading edge 318 of each guide vane 314 is oriented to have asubstantially zero angle of attack to the incoming flow of fluid, saidfluid flows over both the low pressure side 324 and high pressure side326 of the guide vane 314 and is guided to flow in an axial directionrelative to the spoke members 116′ without separating from the guidevane 314 or associated spoke member 116′. Pressure losses incurred byfluid flowing through the upper rotor disc 80′ are thereby avoided orminimised.

A further consequence of the reduction in pressure losses provided bythe guide vanes 314 is that the number of spoke members 116′ may beincreased (as compared with the prior art separator 2) withoutundesirably affecting the rate of fluid flow through the separator 2′ asa whole. The increased number of spoke members 116′ allows for greatercompression forces to be transmitted between the frusto-conical part112′ and the hub 114′ of the upper rotor disc 80′. The increased numberof spoke members 116′ can also improve the balance of the upper rotordisc 80′.

It is to be noted that FIG. 22 represents a schematic view of thecross-section of a guide vane 314 and associated spoke member 116′ , andis not necessarily representative of a particularly preferred geometryor indeed of particularly preferred rotary speeds and fluid flow rates.

With reference to FIG. 21, a cylindrical nm 328 will be seen providedconcentrically with, and upstanding from, the radially inner most edge312 of the frusto-conical part 112′. In the assembled separator 2′, therim 328 locates radially outward from the downwardly projectingcylindrical wall 58′ of the top bearing unit 50′. The rim 328nevertheless locates in close proximity with said cylindrical wall 58′so as to prevent (or significantly restrict) a leakage of fluidtherebetween (see FIG. 34 in particular).

Three splines 254 extend radially from the hub 114′ of the upper rotordisc 80′ as will be most readily seen from FIG. 23 of the accompanyingdrawings. The three splines 254 are spaced equi-distant about thecentral longitudinal axis of the upper rotor disc 80′ and extend axiallyalong the hub 114′ (and, consequently, along the rotary shaft 78′) froma lower side 330 of the spoke members 116′ to a point along the hub 114′which, in the assembled separator 2′, locates approximately mid-wayalong the central hub element 292 of the fan disc 240.

Each spline 254 has a root portion 350 and a tip portion 352. The rootportion 350 joins with the remainder of the hub 114′. The tip portion352 adjoins with the root portion 350 and provides a free end to thespline 254. The root portion 350 of each spline 254 is wider (i.e. has agreater circumferential dimension) than the tip portion 352. As aconsequence of the different widths of the root and tip portions350,352, a step 354 is provided on either side of each spline 254 at thejunction between the root and tip portions 350,352. With reference toFIG. 23 in particular, it will be seen that the width of the rootportion 350 of each spline 254 increases from a lower end of each spline254 to an upper end of each spline 254. Furthermore, the width of eachroot portion 350 is approximately equal to the width (i.e. thecircumferential dimension) of one of the twelve spokes 116′ of the upperrotor disc 80′. The tip portion 352 of each spline 254 is alsocircumferentially aligned with a spoke member 116′ and adjoinedtherewith.

The hub 120′ of each separator disc 82′ has an aperture 252 throughwhich the rotary shaft 78′ and upper rotor disc hub 114′ extend (seeFIGS. 23, 24 and 25 in particular). Rotational movement of the separatordisc hub 120′ relative to the upper rotor disc hub 114′ (and, therefore,relative to the rotary shaft 78′) is prevented by means of three splines254 which are provided axially along the length of the upper rotor dischub 114′ and extend radially into a corresponding female mating profiledefined by the aperture 252 of the separator disc hub 120′. Thislocation of the splines 254 prevents lateral and rotational movement ofa separator disc hub 120′ relative to the rotary shaft 78′. Morespecifically, surfaces 356 of the tip portion 352 of each spline 254(which surfaces 356 extend generally radially) abut with correspondingsurfaces 358 (which surfaces 358 also extend generally radially) of saidmating profile to prevent relative rotation of a separator disc 82′ andthe upper rotor disc hub 114′ (and rotary shaft 78′). It will beappreciated that the abutting surfaces 356,358 press against oneanother, in use, in a direction generally perpendicular to each of saidsurfaces 356,358 and, for this reason, there is little or no relativesliding movement of said surfaces 356,358 and little or no associatedfrictional wear of said surfaces 356,358 which can lead to an increasedor undesirable relative rotation between a separator disc 82′ and theupper rotor disc hub 114′.

The separator disc hub 120′ of each separator disc 82′ is connected tothe frustoconical part 124′ of each separator disc 82′ by means oftwelve radially extending spoke members 126′. As in the prior artseparator 2′, the spokes 126′ (and the remainder of the associatedseparator disc 82′) are made of a relatively thin and resilientlyflexible plastics material. Again, as in the prior art separator 2′, thespokes 126′ are capable of resisting the lateral and rotational forcesto which they are subjected without deforming, and the compression forcegenerated by the helical spring 96′ is transmitted through the separatordisc stack 84′ via the spacers 246 rather than by the separator discspokes 126.

It will also be understood by the skilled person that the relativegeometry of the splines 252 and the aperture 252 of each separator disc82′ ensures that, as mentioned above, each separator disc 82′ islocatable on the rotary shaft 78′ in one of only three angularpositions. By virtue of the positioning of the spacers 246 relative tothe aperture 252, the polar or angular positioning of spacers 246 of theseparator discs 82′ remain the same, relative to the rotary shaft 78′,regardless of which of the three angular positions is used and,accordingly, there is no possibility of the separator disc stack 84′being assembled on the rotary shaft 78′ with the spacers 246 of adjacentseparator discs 82′ being misaligned. Nevertheless, each separator disc82′ is provided with a marker which may be aligned with the markers ofother discs 82′ in the disc stack 84′. In this way, all the discs 82′within the stack 84′ will have the same angular position relative to therotary shaft 78′. The marker is provided as a rib 256 located on the hubbetween two spokes 126′ and extending a short distance radially outward.

For the purposes of clarity, FIGS. 13, 15, 19, 20, 27, 33, 34 of theaccompanying drawings show a disc stack 84′ with a reduced number ofseparator discs present.

An annular recess 258 (see FIG. 21) concentric with the rotary shaft 78′is provided in an upper surface of the upper rotor disc hub 211′. Theannular recess 258 receives a second helical compression spring 130′ andprevents downward axial movement of this spring 130′ along the rotaryshaft 78′. Furthermore, in the assembled separator 2′, the cage of thecaged bearings 52′ abuts and downwardly compresses the second spring130′ (with the upper end of the rotary shaft 78′ remaining spaced fromthe cap member 54′ of the top bearing unit 50′—see FIG. 34 inparticular).

During assembly of the improved separator 2′, all but the combined fanand turbine unit 88′ of the second group of internal components areinterconnected with one another. The upper rotor hub 114′ (and theremainder of the upper rotor disc 80′) is injection moulded with therotary shaft 78′ in-situ. The stack 84′ of separator discs 82′ is thenslid axial along the rotary shaft 78′ from a lower end thereof so as tolocate in abutment with the underside of the frusto-conical part 112′ ofthe upper rotor disc 80′.

Before the fan/turbine unit 88 is mounted to the lower end of the rotaryshaft 78, the lower end of the shaft 78 is located through a centralcircular aperture provided in each of the bearing plate 70 and housinginsert 72 of the first group of internal components. In so doing, thelower end of the rotary shaft 78 is also extended through the bottombearing unit 90 which is secured to the central aperture of the bearingplate 70 (see FIGS. 8 and 10 in particular).

With further regard to the compression force applied to the separatordisc stack 84′, it will be understood by the skilled person that thisforce is generated by the helical compression spring 96′. During use ofthe separator 2′, the compression spring 96′ rotates with the rotaryshaft 78′ and a lower end of the compression spring 96′ abuts with aradially inner race of the bottom bearing unit 90′ so as to pressthereagainst and transfer said force upwardly to the splash guard hub308. The compression force is then transmitted from the splash guard hub308 to the end plate hub 98′. A rotation of the splash guard 242relative to the end plate 86′ is resisted due to frictional forcesbetween the splash guard hub 308 and the end plate hub 98′ (which willbe understood to be a function of the compression force).

Due to the rigidity of the end plate 86′, the compression force istransmitted from the hub 98′ to the frusto-conical part 108′ of the endplate 86′ via said plurality of radially extending spoke members 110′.The compression force is then transmitted to the caulk members 298 ofthe fan disc 240 via the frusto-conical part 108′, and then transmittedfrom the frusto-conical part 290 of the fan disc 240 upwardly throughthe stack 84′ (via the spacers 246) to the frusto-conical part 112′ ofthe upper rotor disc 80′. The compression force is transmitted from thefrusto-conical part 112′ to the hub 114′ of the upper rotor disc 80′ viatwelve radially extending spokes 116′. The compression force istransmittable from the frusto-conical part 112′ to the hub 114′ due tothe rigidity of the upper rotor disc 80′. An axial movement of the upperrotor disc 80′ upwards along the rotary shaft 78′ in reaction to thecompression force is prevented by a location of the upper rotor disc hub114′ in abutment with a downward facing shoulder 250 on the rotary shaft78′. An axial movement of the upper rotor disc 80′ downwards along therotary shaft 78′ is prevented by a location of the upper rotor disc hub114′ in abutment with an upward facing annular shoulder 248 on therotary shaft 78′.

Adjacent discs 82′ of the disc stack 84′ may be, optionally, fixedlysecured to one another. This will tend to increase the rigidity of thedisc stack 84′ and ensure the relative rotational positions of adjacentdiscs 84′ does not change (i.e. ensure that the disc spacers 246 remainaligned so as to transmit compression force without the space betweenadjacent discs 82′ closing). Discs 82′ may be secured to one another bywelding (for example, ultrasonic welding).

As in the prior art separator 2′, before the fan/turbine unit 88′ ismounted to the lower end of the rotary shaft 78′, the lower end of theshaft 78′ is located through a central circular aperture provided ineach of the bearing plate 70′ and housing insert 72′ of the first groupof internal components. The lower end of the rotary shaft 78′ is alsoextended through the bottom bearing unit 90′ which is secured to thecentral aperture of the bearing plate 70′ (see FIGS. 29 and 30 inparticular).

The combined fan and turbine unit 88′ is secured to the lower end of therotary shaft 78′ which projects downwardly from the underside of thebearing plate 70′. The fan/turbine unit 88′ is retained in position onthe lower end of the rotary shaft 78′ by means of a circlip 132′(retained in a circumferential recess in the lower end of the rotaryshaft 78′) and a helical compression spring 360 located about the lowerend of the rotary shaft 78′ and abutting an upwardly facing surface ofthe circlip 132′.

The circlip 132′ and compression spring 360 locate within a cavity ofthe combined fan and turbine unit 88′. The compression spring 360presses upwardly within said cavity so as to bias the fan/turbine unit88 upwardly into contact with a radially inner race of the bottombearing unit 90′. This arrangement is most clearly evident from FIG. 30of the accompanying drawings. With reference to this Figure, it will beunderstood that an upwardly facing deflector surface 139′ is provided onsaid unit 88′ and is located radially inwardly of fan blades 140′ ofsaid unit 88′. The deflector surface 139′ performs the same function asthe deflector washer 139 in the prior art separator 2, but is providedintegrally with the fan/turbine unit 88′ rather than as a separateabutting component. A radially inner part of the deflector surface 139′is pressed upwardly into abutment with an inner bearing race of thebottom bearing unit 90′ which, in turn, is pressed upwardly against thebearing plate 70′. The deflector surface 139′ and the radially outerbearing race of the bottom bearing unit 90′ are axially spaced from oneanother so as to allow for a flow of separated oil downwardly throughthe bottom bearing unit 90′ and radially outwardly through said axialspacing into the turbine casing.

The rotor assembly of the separator 2 is rotated in a directionindicated by arrow 134′ (see FIGS. 29 and 30) by means of a hydraulicimpulse turbine. As in the prior art separator 2′, the fan/turbine unit88′ comprises a Pelton wheel 136′ having a plurality of buckets 138′evenly spaced along the circumference thereof In use of the separator2′, a jet of oil is directed from a nozzle (not shown) within theturbine casing towards the circumference of the Pelton wheel 136′. Morespecifically, the jet is directed along a tangent to a circle passingthrough the plurality of buckets 138′ so that the jet enters a bucketaligned with a surface thereof The jet flows along said surfacefollowing the internal profile of the bucket and is thereafter turned bysaid profile to flow along a further surface and be thereafter ejectedfrom the bucket. The result is that the jet rotates the wheel 136′.

A fan having a plurality of blades 140′ is also integrally formed withthe wheel 136′. The blades 140′ are located on the wheel 136′ in closeproximity to the underside of the bearing plate 70′. The plurality offan blades 140′ are also in approximately the same axial position alongthe rotary shaft 78′ as the deflector surface 139′ and the bottombearing unit 90′. The fan blades 140′ extend radially outward fromadjacent the bottom bearing unit 90′. It will be understood by thoseskilled in the art that the fan blades 140′ rotate about the centralaxis 64′ as the turbine wheel 136′ is rotated. In so doing, the fanblades 140′ effectively throw fluid from the region between the wheel136′ and the underside of the bearing plate 70′, thereby reducing thefluid pressure in the region of the bottom bearing unit 90′ andassisting in drawing separated oil from a location above the bearingplate 70′ downward through the bottom bearing unit and into the turbinecasing below the bearing plate 70′.

For ease of manufacture, the wheel 136′ is made in upper and lower parts142′,144′ and pressed into abutment with one another at line 146′ by twoscrew threaded fasteners (only one of which is shown in FIG. 30 of theaccompanying drawings).

The plurality of fan blades 140′ and the deflector surface 139′ areformed integrally with the upper part 142′ of the fan/turbine unit 88′.The lower part 144′ of the fan/turbine unit 88′ is provided with a lowerplate member 364 which, in the assembled separator 2′, lies in a planeperpendicular to the central axis 64′ and across the downhole opening tothe flow path 92′ of the rotary shaft 78′. The plate member 364 isnevertheless spaced from said opening to the flow path 92′ so as toallow a flow of fluid into said opening.

The plate member 364 is provided with four apertures 366 which, in theassembled separator 2′, are located equi-distant along an imaginarycircle centred on the central axis 64′. It will be understood by askilled person that an alternative number of apertures 366 may be used,although the apertures should be arranged so as to ensure a rotarybalancing of the fan/turbine unit 88′.

Significantly, the apertures 366 are located radially outwardly from theopening to the flow path 92′. It will be understood therefore that thearrangement is such that a mist of oil droplets may flow upwardlythrough the apertures 366 from the turbine casing and thereby enter thecavity within the fan/turbine unit 88′ and flow upwardly through theflow path 92′ of the rotary shaft 78′. It will, however, also beappreciated that the flow from the apertures 366 to said opening of theflow path 92 is in a radially inward direction. During use of theseparator 2′, the fan/turbine unit 88′ is of course rotating in thedirection indicated by arrow 134′ and, whilst a mist of oil droplets mayflow radially inward from the apertures 366 to the flow path 92′,comparatively larger bodies of oil flowing through the apertures 366will be moved in a lateral direction by the spinning plate member 364and tend to be thrown outwards away from the opening to the flow path92′. For example, in the event of a vehicle leaning or otherwise movingin such a way as to splash oil upwardly from the turbine casing throughthe apertures 366 so as to flood the cavity of the fan/turbine 88′, thelateral motion imparted on the oil within said cavity tends to preventsaid oil from flowing inwardly towards the rotary shaft 78′. Anundesirable flow of large quantities of oil upwardly through the rotaryshaft 78′ and into the disc stack 84′ is therefore avoided.

Two drain apertures 368 are provided in the plate member 364 so as toallow oil to drain from the cavity within the fan/turbine unit 88′ backinto the turbine casing. The drain apertures 368 are locateddiametrically opposite one another and form a slot in the plate member364 and in a generally cylindrical wall upstanding from the circularperimeter of said plate member 364. The location of the drain apertures368 in a radially outer most part of the turbine cavity ensures that oilthrown to the outer perimeter of said cavity away from the rotary shaft78′ does drain effectively from the fan/turbine unit 88′.

Whilst the plate member 364 is shown in the embodiment of FIGS. 29 and30 as being integral with the lower part 144′ of the fan/turbine unit88′, in an alternative embodiment shown in FIGS. 31 and 32 of theaccompanying drawings, the end plate 364 is provided as a circular discseparate to the lower part 144 of the fan/turbine unit 88′. Withreference to FIGS. 31 and 32, it will be seen that the separate platemember 364 of the alternative embodiment is a circular disc providedwith apertures 366 in the same way as in FIGS. 29 and 30. However, thealternative plate member 364 is secured in position relative to theremainder of the fan/turbine unit 88′ by the screw threaded fasteners362 (which extend therethrough) and is absent of the drain apertures368. In this alternative arrangement, the drain apertures 368 areprovided solely in the cylindrical wall of the lower part 144′ which isarranged concentrically with the circular perimeter edge of the platemember 364 and extends upwardly therefrom. The lower part 144′ of thefan/turbine unit 88′ is further provided with a second cylindrical wall370 which is located within the cavity of the fan/turbine unit 88′ andextends downwardly to provide a downwardly facing annular surfaceagainst which the plate member 364 may be pressed by the two screwthreaded fasteners 362. Recesses are provided in the downwardly facingannular surface so as to provide a fluid pathway 372 between saidcylindrical wall 370 and the plate member 364. In use, oil flowingoutwardly across the upper surface of the plate member 364 passes to thedrain apertures 368 via the flow path 372.

Whilst the fan/turbine unit 88′ of FIGS. 31 and 32 is provided with anouter cylindrical wall and a plate member 364 which together define acavity and is additionally also provided with a further cylindrical wall370 against which the plate member 364 is located, the fan/turbine unit88 is in other respects similar to that of the prior art separator 2 andis secured to the rotary shaft 78′ in the same way as in the prior artseparator 2. Specifically, the fan/turbine unit 88′ is secured to therotary shaft 78′ by means of a washer 133′ which presses upwardly on thelower part 144′ of said unit 88′ and is retained in position by means ofa circlip 132 located in a circumferential recess on the exteriorsurface of the rotary shaft 78′. It will be understood that the washer133′ and circlip 132 provide an alternative securing means to thecompression spring 360 and circlip 132 shown in FIGS. 29 and 30.

With regard to the first group of internal components, the bearing plate70′ has a circular shape with a diameter substantially equal to thediameter of the rotor housing 4′ . As in the prior art separator 2′, therelative geometries are such as to allow the bearing plate 70′ to locateon a downwardly facing shoulder 148′ at a lower end of the rotor housing4′. In this way, the lower open end of the rotor housing 4′ is closed bythe bearing plate 70′. However, in the improved separator 2′, the loweropen end of the rotor housing 4′ abuts the upper side of the bearingplate 70′ and is provided with a circumferential recess 260 forreceiving an O-ring seal 262 (see FIG. 34). It will be understood thatthe second O-ring seal 262 ensures a fluid seal between the rotorhousing 4′ and the bearing plate 70′.

Furthermore, in the assembled separator 2′, the radially outermostcircumferential edge surface 630 (forming a datum surface) of thebearing plate 70′ registers in abutment with a cylindrical inner surface632 encircling the lower open end of the rotor housing 4′. In this way,the bearing plate 70′ is laterally aligned in a desired final positionrelative to the rotor housing 4′ (see FIG. 13).

The bearing plate 70′ is also provided with a central circular aperturewhich, in the assembled separator 2′, is concentric with the rotorhousing 4′. In other words, in the assembled separator 2′, the circularcentral aperture of the bearing plate 70′ is centered on the centralaxis 64′ of the rotor housing 4′. Furthermore, as will be particularlyevident from FIG. 34 of the accompanying drawings, the bottom bearingunit 90′ is received in the central aperture of the bearing plate 70′.The radially outermost part of the bottom bearing unit 90′ is fixedrelative to the bearing plate 70′. The radially innermost part of thebottom bearing unit 90 is located adjacent the rotary shaft 78′, but isnot fixed thereto.

As mentioned above, the first group of internal components alsocomprises a housing insert 72′ which is fixedly secured to the bearingplate 70′. As in the prior art separator 2′, the housing insert 72′functions to segregate cleaned gas from oil which has been separatedtherefrom. The housing insert 72′ of the improved separator 2′ alsoprovides an outlet 150′ for cleaned gas, which sealingly connectsdirectly with the cylindrical inlet portion 211 of the valve unithousing 12′ (see FIG. 15).

The housing insert 72′ is provided as a unitary moulding of plasticsmaterial. However, in describing the housing insert 72′ below, theinsert will be considered as comprising four portions: an outerdeflector wall 264 having a frusto-conical shape; a support wall 266having a cylindrical shape; a segregating roof member 268 having afrusto-conical shape; and an outlet portion 270 defining said insertoutlet 150′ (see FIGS. 27 and 28 in particular).

The segregating roof member 268 of the housing insert 72′ has afrusto-conical shape and is supported on the support wall 266. Thesegregating roof member 268 is provided with a central circular aperturewhich, in the assembled separator 2′, has a central axis coincident withthe central axis 64′ of the rotor housing 4′. An elongate channel/recess272 (see FIG. 28) is provided in the upper surface of the segregatingroof member 268. This channel/recess 272 defines a fluid pathway forcleaned gas which extends from an inlet 282 of the recess 272 to theoutlet portion 270 (having a tubular shape) of the housing insert 72′.The inlet 282 is defined by a recessed circumferential portion of anupper circular perimeter edge 274 of the segregating roof member 268.The inlet 282 is located generally diametrically opposite the outletportion 270 of the housing insert 72′. The aforementioned recessedportion of said perimeter edge 274 extends through an arc 280 ofapproximately 80°, which arc is centred on said central axis of thehousing insert aperture. In alternative embodiments, an inlet to thefluid pathway may be define by a recessed portion in said perimeter edge274 which extends through a different arc, for example between 45° and110°. In the assembled separator 2′, only a small distance spaces thesegregating roof member 268 from the end plate 86′. As a consequence, itis believed that the majority of cleaned gas entering the region 606between the segregating roof member 268 and the end plate 86′ does sothrough the space between the aforementioned recessed portion of saidperimeter edge 274 and the end plate 86′, with only a relatively smallproportion of cleaned gas flowing into said region past the remainder ofsaid perimeter edge 274.

It will be understood therefore that the space between the entirecircumferential perimeter edge 274 and the end plate 86′ provides aninlet 610 to said region 606 between the segregating roof member 268 andthe end plate 86′, but that because one lengthwise portion 612 (i.e. theinlet 282 to the channel/recess 272) of this inlet 610 has a greaterdepth 613 (i.e. a greater axial spacing between the perimeter edge 274and the end plate 86′) than other lengthwise portions of the inlet 610,a large proportion of cleaned gas flowing into said region 606 does sothrough said lengthwise portion 612 having the greater depth 613. Thedepth of the remaining lengthwise portions of said region inlet (610) isminimal so as to minimise the flow of fluid therethrough and therebyalso minimise the passage of oil droplets therethrough. The depth of theremaining lengthwise portions may be between a tenth and a half of thegreater depth 613, and is preferably one third of said greater depth613.

During use of the separator 2′, cleaned gas exiting the separator discstack 84′ flows downwardly in a spiralling rotary motion along theinterior surface of the cylindrical wall of the rotor housing 4′. Itwill be understood therefore that cleaned gas entering theaforementioned region 606 between the segregating roof member 268 andthe end plate 86′ tends to do so with a rotary swirl motion centred onthe central axis 64′ of the rotor housing 4′. However, the gas flowentering said region 606 via the inlet 282 is immediately guided towardsthe insert outlet 150′ by means of the side walls 276, 278 of theelongate recess 272. This guidance of the cleaned gas flow is alsobelieved to reduce the rotary swirl motion of cleaned gas immediatelyupon entry of said gas into said elongate recess 272 via the recessinlet 282. In this regard, it will be seen from FIG. 28 of theaccompanying drawings that the upstream portion of the elongate recess272 is curved (the side walls 276,278 of the recess 272 thereby aligningwith the swirling inlet fluid so as to substantially minimise desirableunpressure losses as fluid initially impacts the sidewalls 276,278) andprogressively straightens as fluid moves downstream along the recess 272towards the insert outlet 150′. It is believed that the immediatereduction of swirl motion in the majority of clean gas entering theregion between the segregating roof member 268 and the end plate 86′significantly reduces pressure losses in fluid flowing through this partof the separator 2′ as compared with the prior art separator 2 describedabove.

It will be appreciated that cleaned gas which does not flow through theinlet 282 but which enters the region between the segregating roofmember 268 and the end plate 86′ at other locations along the perimeterof the segregating roof member 268 will tend to flow through said regionwith a swirling motion until received by the elongate recess 272whereupon the radially outer sidewall 276 in particular will, it isbelieved, guide the fluid towards the insert outlet 150′ and also reducethe swirling motion of said fluid.

The cylindrical support wall 266 is concentrically arranged with thecentral circular aperture in the segregating roof member 268 andprojects downwardly from the underside of the segregating roof member268. The diameter of the support wall 266 is less than that of theperimeter edge 274 of the segregating roof member 268. In the assembledseparator 2′, a lower downwardly facing circular edge 450 (see FIG. 27)of the support wall 266 abuts with the bearing plate 70′ at a junctiontherebetween. The support wall 266 thereby supports the segregating roofmember 268 on the bearing plate 70′ and ensures a correct axial locationof the segregating roof member 268 relative to the bearing plate 70′.The support wall 266 is also provided with a plurality of cylindricalbosses 452 which each have a recess for threadedly receiving a fastener74′. In the assembled separator 2′, each fastener 74′ extends into oneof said bosses 452 from below the bearing plate 70′ through an aperturein the bearing plate 70′. In this way, the insert housing 72′ is fixedlysecured to the bearing plate 70′.

The lower downwardly facing circular edge 450 of the support wall 266 isprovided with a plurality of apertures/recesses 454 positioned atvarious locations along said edge 450. As will be seen from FIGS. 27 and34 in particular, the recesses 454 provide a space between the supportwall 266 and the bearing plate 70′ through which, during use of theassembled separator 2′, fluid may flow. Specifically, during use of theseparator 2′, separated oil flowing radially inwardly from thecylindrical wall of the rotor housing 4′ along the bearing plate 70′passes through the plurality of recesses 454. A proportion of cleanedgas also flows radially inwardly across the upper surface of the bearingplate 70′ (as will be understood by a skilled reader) and this fluidalso flows through the plurality of recesses 454. This flow of fluid isdenoted by arrow 188′ in FIG. 34.

The outer deflector wall 264 extends downwardly from the perimeter edge274 of the segregating roof member 268. The deflector wall 264 has afrusto-conical shape diverging in a downward direction from thesegregating roof member 268 towards the bearing plate 70′ in theassembled separator 2′. The diameter of the deflector wall 264 at anupper end thereof (and, therefore, the diameter of the perimeter edge274 of the segregating roof member 268) is substantially equal to theouter diameter of the separator disc stack 84′. Due to thefrusto-conical shape of the deflector wall 264, the deflector wall 264converges with the generally cylindrical wall of the rotor housing 4′when moving in a downward direction. The cross-sectional area of theflow path between the deflector wall 264 and the rotor housing 4′therefore reduces in the direction of flow (i.e. in a downwarddirection). The lower free end 608 of the deflector wall 264 is locatedspaced from the cylindrical wall of the rotor housing 4′ and a distance456 of between 2 millimeters and 200 millimeters, and of preferably 14millimeters, above the bearing plate 70′. This spacing of the outerdeflector wall 264 from the rotor housing 4′ and the bearing plate 70′allows for separated oil (or other separated material) and cleaned gas(which has not entered the first region inlet 610) to flow downwardlyalong the cylindrical wall of the rotor housing 4′ and radially inwardlyalong the bearing plate 70′ past the deflector wall 264 (including itsfree end). In so doing, the separated oil and cleaned gas flows througha second region 614 on an opposite side of the housing insert 72′ to thefirst flow region 606.

Also, due to its frusto-conical shape, the outer deflector wall 264diverges from the cylindrical support wall 266 when moving in a downwarddirection. The outer deflector wall, segregating roof member 268 andcylindrical support wall 266 define a generally annular shaped cavity458 (see FIG. 34) with an open lower end. The arrangement is such as toreduce the likelihood of separated oil flowing downwardly along therotor housing 4′ past the inlet 282 of the recess 272, only tosubsequently flow upwardly due to a recirculation of fluid and therebyflow into said inlet 282 contaminating cleaned gas.

More specifically, whilst the relatively large spacing between the rotorhousing 4′ and the upper end of the deflector wall 264 allows for aready entry of separated oil between these features, the comparativelysmall spacing between these features at the lower free end of thedeflector wall 264 reduces the ease with which separated oil may besplashed or re-circulated upwardly between said free end and the rotorhousing 4′. Furthermore, any recirculation of fluid adjacent theradially outer perimeter of the bearing plate 70′ will tend to result inseparated oil flowing into the aforementioned cavity 458. For example,separated oil may flow upwardly along the radially outer surface of thecylindrical support wall 266, outwardly along the underside of thesegregating roof member 268, and then downwardly along the radiallyinner surface of the deflector wall 264. In due course, the oil willlikely fall from the cavity 458 onto the bearing plate 70′ under theaction of gravity. It will be appreciated that this re-circulating flowpath does not result in separated oil flowing upwardly in such a way asto risk the contamination of the cleaned gas flowing into the regionbetween the segregating roof member 268 and the end plate 86′. Thus,once cleaned gas has flowed past the region 606 inlet (i.e. the inlet tobetween the segregating roof member 268 and the end plate 86′) towardsthe bearing plate 70′, any subsequent re-circulation of said gas backupstream towards said inlet is prevented from resulting in re-circulatedgas (and oil droplets carried thereby) entering said region 606 by thedeflector wall 264, which effectively segregates (i.e. maintainsseparation of) said re-circulated gas from said inlet.

The outlet portion 270 of the housing insert 72′ is provided as acylindrical tubular element opening onto the upper surface of thesegregating roof member 268 (and, more specifically, opening into therecess 272 for receiving cleaned gas) and extending in a generallyradially outwards direction through the support wall 266 and the outerdeflector wall 264. As will be particularly evident from FIGS. 13 and 14of the accompanying drawings, the outlet portion 270 is positioned abovethe downwardly facing edge of the support wall 266. Accordingly, in theassembled separator 2′, the outlet portion 270 is located above thebearing plate 70′ so that fluid may flow beneath the outlet potion 270.Advantageously, separated oil may flow beneath the outlet portion 270and does not, therefore, tend to climb up the outer surface of theoutlet portion 270 towards the perimeter edge 274 of the segregatingroof member 268 where separated oil may readily contaminate clean gasflowing into the recess 272 of the housing insert 72′. A free end of theoutlet portion 270 distal to the end thereof opening into the recess 272is provided with a support element 460 which projects downwardly fromthe lowermost part of said free end so as to abut the bearing plate 70′.In this way, the support element 460 assists in maintaining a minimumspacing between the bearing plate 70′ and the outlet portion 270, andalso allows the bearing plate 70′ to provide support to the free end ofthe outlet portion 270.

During assembly, the separator 2′ is secured to a turbine casing (notshown) in a similar way as described above in relation to the prior artseparator 2′. Specifically, the improved separator 2′ is secured to aturbine casing by means of four threaded fasteners (not shown), each ofwhich passes through a different one of four bosses 284 integral withthe lower end of the rotor housing 4 (see FIGS. 18 and 29 inparticular).

It will be understood by those skilled in the art that, as in the caseof the prior art separator 2, the bearing plate 70′ (and, therefore, allof the components of the first and second groups) is retained in therequired position relative to the rotor housing 4′ by virtue of theturbine casing pressing the bearing plate 70′ into abutment with thedownwardly facing shoulder 148′ when the rotor housing 4′ and turbinecasing are fastened to one another. The bearing plate 70′ is essentiallyclamped between the rotor housing 4′ and the turbine casing 178′ bymeans of the threaded fasteners extending through the four bosses 284.As the threaded fasteners are tightened and the bearing plate 70′ isbrought into abutment with the shoulder 148′ as a consequence, theO-ring seal 262 at said shoulder 148′ is pressed in the associatedrecess 260 and the second helical compression spring 130′ is compressedby the top bearing unit 50′.

In operation of the improved separator 2′, a nozzle (not shown) in theturbine casing directs a jet of oil onto the turbine wheel 136′ so as torotate the turbine wheel in the direction indicated by arrow 134′(seeFIGS. 29 and 34). This rotation of the turbine wheel drives a rotationof the rotor assembly as a whole in the direction of arrow 134′ aboutthe central axis 64′ of the rotor housing 4′. In other words, the rotaryshaft 78′; the upper rotor disc 80′; the stack 84′ of separator discs82′; the fan disc 240; the end plate 86′; the splash guard disc 242; andthe combined fan and turbine unit 88′ (i.e. collectively referred toherein as the rotor assembly) rotate together as a unitary assemblywithin the rotary housing 4′ and relative to said housing 4′ and thebearing plate 70′; the housing insert 72′; and the turbine casing.

Gas vented from the engine casing, and requiring treatment by theseparator 2′, is introduced into the separator 2′ via the fluid inlet 8′located at the top of the rotor housing 4′. As indicated by arrow 68′ inFIG. 34, the inlet gas enters the rotor housing 4′ in a directionparallel with, and in line with, the central axis 64′ and flows throughthree slots 66′ in the top bearing unit 50′ before flowing into theinlet 600 of the rotor assembly past the twelve spokes 116′ of the upperrotor disc 80′. The rotational movement of the twelve spokes 116′ alsoresults in a lateral movement of the fluid located between said spokesin that said fluid moves tangentially from the circular path of thespokes 116′ and is effectively thrown outwards towards the cylindricalwall of the rotor housing 4. In essence, the twelve spokes 116′ impart acylindrical motion onto the inlet gas.

As inlet gas flows downwardly through the spokes 116′,126′ of the upperrotor disc 80′ and the separator discs 82′, the gas is moved laterallytowards the cylindrical wall of the rotor housing 4′ via the spaces 602between adjacent separator discs 82′, as shown by arrows 184′ in FIG.34. By following this path, the direction of fluid flow is changed bymore than 90°.

It will be understood that the spaces 604 between the radially outermost circumferential edges of adjacent separator discs 82′ collectivelyrepresent an outlet from the rotor assembly.

It will also be understood by those skilled in the art that oil droplets186′ tend to collect together and form larger droplets as they moveacross the separator discs and are thrown onto the cylindrical wall ofthe rotor housing 4′. Once received by said cylindrical wall, the oildroplets 186′ tend to run downwardly under the action of gravity ontothe bearing plate 70′. The outer most circumferential edge of theseparator stack 84′ is sufficiently inwardly spaced from the cylindricalwall of the rotor housing 4′ so as to allow oil droplets to rununimpeded downwardly onto said bearing plate 70′. The O-ring seal 262ensures oil droplets cannot flow between the bearing plate 70′ and therotor housing 4′.

It will be understood by those skilled in the art that, because of therotary motion of the rotor assembly, the fluid pressure within the rotorhousing 4′ is greater at the peripheral edge of the separator disc stack84′ and bearing plate 70′ than in the region enclosed by the supportwall 266 and roof member 268 of housing insert 72′ and the bearing plate70′. As a consequence, there tends to be a flow of cleaned gasdownwardly along the cylindrical wall of the rotor housing 4′ andradially inwardly along the bearing plate 70′. This fluid flow tends topush separated oil droplets downwardly along the cylindrical wall ontothe bearing plate 70 below and then radially inwardly along the bearingplate 70′ through the apertures in the support wall 266 of the housinginsert 72′. This gas fluid flow is indicated by arrow 188′ (see FIG.34). The gas fluid flow moves radially inwardly across the upper surfaceof the bearing plate 70′ towards the central circular aperture in thehousing insert 72′. This flow across the bearing plate 70′ tends to pushseparated oil droplets across the bearing plate 70 towards the bottombearing unit 90′, through which said oil droplets pass. The rotating fanblades 140′ of the combined fan and turbine units 88′ tend to lower thestatic pressure in the turbine casing (to which the rotor housing 4′ isattached during use) in the region of the bottom bearing unit 90′ so asto draw oil droplets through the bottom bearing unit 90′. The fan blades140′ then throw said droplets radially outwardly into the turbinecasing, from where they may be returned to the engine crank casing.Meanwhile, the gaseous fluid flowing across the bearing plate 70′ isdrawn upwardly through the central aperture of the insert housing 72′ topass radially outwardly between the end plate 86′ and the fan disc 240.The gaseous fluid may then exit the rotor housing 4′ by flowing throughsaid cylindrical portion 211 of the valve unit housing 12′, which issealingly connected to the housing insert 72′ and passes through thehousing insert outlet 150′ and the rotor housing outlet 10′.

It will also be appreciated with reference to the accompanying drawingsthat, as well as flowing over the upper surface of the bearing plate 70′and through the apertures in the support wall 266 of the housing insert72′, some of the cleaned gas flows to said cylindrical portion 211 viaan alternative route between the underside of the end plate 86′ and theupperside of the segregating roof member 268 of the housing insert 72′.This alternative route is indicated by arrow 190′.

It will be appreciated that, as in the prior art separator 2, the flowof oil through the bottom bearing unit 90′ of the improved separator 2′has a beneficial lubricating effect on the bearing unit. The top bearingunit 50′ is similarly lubricated by an oil mist which naturally occursin the turbine casing and which is transported upwards to the topbearing unit 50′ through the longitudinal flow path 92′ extendingthrough the rotary shaft 78′.

Either the prior art ALFDEX™ separator 2 or the improved separator 2′described above may incorporate an alternative means for rotating therotary shaft 78′ as shown in FIG. 35 of the accompanying drawings. Withreference to FIG. 35, it will be seen that Pelton wheel turbinepreviously described has been replaced by a brushless electric motor380, the rotor 382 of which is secured to a lower end of the rotaryshaft 78″ below the bearing plate 70″. The electric motor 380 is shownin FIG. 35 driving a prior art ALFDEX™ separator 2. However, as will beunderstood by a person skilled in the art, the electric motor drivearrangement shown in FIG. 35 may also be used in connection with theimproved separator 2′ described above.

With reference to FIG. 35, it will be seen that the electric motor 380of the electric motor drive arrangement is located within a housing 384which is secured to the rotor housing 4 by means of a plurality of screwthreaded fasteners 180′ (only one of which is shown in FIG. 35). Themotor housing 384 is comprised of upper and lower parts 386,388 whichare secured to one another with appropriate fastening means and with anO-ring seal 390 located at the interface therebetween. The O-ring seal390 prevents an undesirable leakage into the space within the housing384 of dirt, water and/or other foreign matter located exteriorly of thehousing 384. In this way, electronic components (including printedcircuit boards and/or other circuitry) are isolated from matter whichmay result in their damage and subsequent malfunction.

The upper part 386 of the housing 384 is provided with a downwardlyprojecting cylindrical wall 392 defining a central aperture in saidupper part 386. The cylindrical wall 392 is arranged to locateconcentrically with the rotary shaft 78″ in the assembled separator. Adeflector washer 139″ is retained on the rotary shaft 78″ by a circlip404″. The deflector washer 139′ thereby presses upwardly against aradially inner bearing race of the bottom bearing unit, as in the priorart ALFDEX™ separator 2. The deflector washer 139″ has a radially outerperimeter edge radially spaced from the cylindrical wall 392 so as toallow for a passage of contaminate oil therebetween.

An upper end of a further separate part 394 of the motor housing 384(having a generally frusto-conical shape) is located at and sealed to alower end of the cylindrical wall 392 of the upper part 386. The sealbetween the cylindrical wall 392 and the frusto-conical part 394 definesa closed loop shape and is provided by means of a further O-ring seal396. A lower end of the frusto-conical part 394 (having a diametergreater than the upper end thereof) is sealed against the lower part 388of the motor housing 384 by means of a yet further O-ring seal 398. Thisseal also defines a closed loop shape.

Thus, on one side of the frusto-conical part 394, said part 394 and thelower part 388 thereby form a space in which the electric motor 380 islocated and into which the lower end of the rotary shaft 78″ extends. Onthe other side of the frusto-conical part 394, said part 394 and theupper part 386 and remainder of lower part 388 form an entirely enclosedand sealed space/compartment 406 in which electronic/electricalcomponents (for example, a Printed Circuit Board 408) are housed forsupplying electrical power and control signals to the electric motor380. The compartment 406 is sealed from not only the exterior of themotor housing 384, but also from the space in which the electric motor380 is located. Contaminate oil which flows through this space in use ofthe separator is therefore prevented from gaining access to theelectronic/electrical components and causing damage thereto.

Furthermore, the frusto-conical part 394 is provided with an aperture(not shown) through which electrical leads 410 (connecting the motor 380and said electrical supply/control components) extend and to which saidleads are sealed.

A connector 412 also extends through an aperture 414 in the motorhousing 384 so as to allow one or more electrical leads (not shown)located to the exterior of the separator (for example, associated with avehicle with which the separator is used) to connect to said electricalsupply/control components housed within the compartment 406. In otherwords, the electrical lead or leads may be provided with a plug formechanically and electrically connecting with the connector 412. Thelead or leads may carry electrical power and/or control signals for theelectric motor drive arrangement. The connector 412 is sealed to thehousing 384 so as to prevent an undesirable ingress of foreign matterinto the compartment 406.

Whilst the compartment 406 has a generally annular shape concentric withthe rotor assembly of the separator, it will be understood that thecompartment 406 may be of a different shape.

A stator 400 of the electric motor 380 is secured to the lower part 388of the motor housing 384. A radially inner portion of saidfrusto-conical part 394, which seals with the cylindrical wall 392,defines an aperture having a diameter substantially equal to theinnermost diameter of the stator 400 of the electric motor 380.

During use of a separator provided with the electric motor drivearrangement of FIG. 35, a supply of electricity is connected to thebrushless electric motor 380 so as to operate the rotor 382 thereof andthereby rotate the rotary shaft 78″. As explained above, separated oilpasses from the rotor housing 4 downwardly through the bottom bearingunit 90. In a separator provided with the electric motor drivearrangement of FIG. 35, this separated oil is ejected from the bottombearing unit into the interior of the motor housing 384, and moreparticular into the space within the cylindrical wall 392 of the upperhousing part 386. The separated oil then passes through the rotor 380 ofthe electric motor 380 and exits the motor housing 384 via a port 402located beneath the electric motor 380 in the lower housing part 388.Oil passing through the rotor 382 (or through a space between the rotor382 and the stator 400) and coming into contact with said rotor 382 andthe stator 400 does not adversely affect the operation of the electricmotor 380 because the electrical leads of the stator 400 are covered bya layer of epoxy lacquer.

With further regard to the manufacture of the improved separator 2′ and,in particular, to the assembly of the top bearing unit 50′ to the rotorhousing 4′, reference is now made to FIGS. 37 to 41 of the accompanyingdrawings. These Figures show a process for spin welding the top bearingunit 50′ to the rotor housing 4′ in a position which is in axialalignment with the bottom bearing unit 90′ when the bearing plate 70′ isassembled in abutment with the lower end shoulder 148′ of the rotorhousing 4′. The assembly process ensures axial alignment of the top andbottom bearing units 50′,90′ despite geometry variations resulting froma warping of the rotor housing 4′ following injection moulding of saidhousing 4′.

The process makes use of a spin welding jig 500 comprising a stator part502 and a rotor part 504 rotatably mounted to the stator part 502. Thestator part 502 comprises a circular disc 506 having a diameter equal tothe bearing plate 70′. The geometry of the circular disc 506 is such asto allow said circular disc 506 to locate in abutment with the rotorhousing 4′ in the same way as the bearing plate 70′ in the assembledseparator 2′ (as shown in FIG. 40). The rotor part 504 comprises a shaft508 which extends through the centre of the circular disc 506 and isoriented perpendicularly to said circular disc 506. The shaft 504 ismounted relative to the circular disc 506 by means of a bearing assembly(not shown).

One end of the shaft 508 is provided with a head 510 for receiving thetop bearing unit 50′. The head 510 is provided as a circular discconcentric with the circular disc 506 of the stator part 502 and centredon the axis about which the rotor part 504 rotates. The diameter of thehead 510 is essentially equal to the diameter of the radially innersurface of the downwardly projecting cylindrical wall 58′ of the topbearing unit 50′. In this way, the cylindrical wall 58′ of the topbearing unit 50′ may locate about the head 510 with little or norelative lateral movement between the top bearing unit 50′ and the shaft508. Relative rotational movement between the top bearing unit 50′ andthe shaft 508 is prevented by projections 512 upstanding from thecircular disc of the head 510. The head 510 comprises three projections512 which are identical to one another and equi-spaced about the rotaryaxis of the shaft 508. The projections 512 are each of a part-circularshape and are positioned and sized so as to locate in the part-circularslots 66′ of the top bearing unit 50′. The projections 512 aresubstantially of the same size and shape as said slots 66′ and, as such,rotational movement of the top bearing unit 50′ relative to the head 510of the shaft 508 is substantially prevented when the projections 512 arereceived by said slots 66 (see FIGS. 37 and 38 in particular).

A second end of the shaft 508 distal to the end provided with the head501 is provided with means 514 for connecting the rotor part 504 to amotor for driving rotary movement of the rotor part 504 relative to thestator part 502.

The spin welding jig 500 with a top bearing unit 50′ located on the head510 thereof is shown in FIG. 39 of the accompanying drawings. With thetop bearing unit 50′ located on the head 510, the shaft 508 and topbearing unit 50′ are inserted into a rotor housing 4′ as shown in FIG.40. The circular disc 506 is located in abutment with the lower shoulder148′ of the rotor housing 4′. More specifically, a radially outermostcircumferential edge surface 634 (forming a datum surface) of thecircular disc 506 registers in abutment with the cylindrical innersurface 632 encircling the lower open end of the rotor housing 4′. Inthis way, the lateral positioning of the top bearing unit 50′ relativeto the rotor housing 4′ is determined. With the spin welding jig 500located in this way within the rotor housing 4′, the rotational axis ofthe rotor part 504 is coincident with the previously described centralaxis 64′ of the rotor housing 4′.

The rotor part 504 may be arranged so as to be moveable relative to thestator part 502 in an axial direction so that the top bearing unit 50′may move from a first position, in which said bearing unit 50′ is spacedfrom the upper part of the rotor housing 4′, to a second position, inwhich the bearing unit 50′ is pressed into abutment with the ridge 238provided on the rotor housing 4′ (see FIG. 34). During assembly of thetop bearing unit 50′ to the rotor housing 4′, the rotor housing 4′ isheld stationary and, whilst the circular disc 506 of the stator part 502is located in abutment with the lower shoulder 148′ of the rotor housing4′, the rotor part 504 is rotated at relatively high speed and movedaxially further into the rotor housing 4′ so as to bring aspinning/rotating top bearing unit 50′ into contact with said ridge 238.The spinning top bearing unit 50′ is pressed forcefully against theridge 238 so as to generate friction heat and thereby melt the abuttingsurfaces of plastics materials of the top bearing unit 50′ and the ridge238. Whilst pressing the bearing unit 50′ against the ridge 238, therotary motion of the shaft 508 is rapidly reduced and stopped so as toallow the bearing unit 50′ and ridge 238 to bond with one another as themelted plastics materials cool. The top bearing unit 50′ and rotorhousing 4′ are thereby spun welded to one another.

The rotor housing 4′ may be held stationary during the spin weldingprocess by means of screw threaded fasteners extending through bosses284 in the rotor housing 4′ and into a cylindrical mounting block 516(see FIG. 40).

Once the top bearing unit 50′ has been secured to the rotor housing 4′,the spin welding jig 500 may be removed from the rotor housing 4′. Thetop bearing unit 50′ is thereby left correctly positioned and secured tothe rotor housing 4′ as shown in FIG. 41 of the accompanying drawings.It will be understood that the top bearing unit 50′ is located in aposition which is central relative to the lower circular shoulder 148′of the rotor housing 4′. Accordingly, when the internal components ofthe separator 2′ are located within the housing 4′, the abutment of thebearing plate 70′ against said shoulder 148′ ensures that the bottombearing unit 90′ also locates centrally with said shoulder 148′. The topand bottom bearing units 50′ ,90′ are thereby axially aligned despiteany previous warping of the rotor housing 4′ subsequent to injectionmoulding.

The versatility of the improved separator is enhanced as compared to theprior art separator 2 by virtue of certain modules/components thereofbeing interchangeable in different separator systems (see FIG. 36). Theability of the rotor housing 4′ (i.e. one particular type of module) toreceive different valve units 14′ (i.e. different versions of anothertype of module) has already been discussed above. This modular approachis achieved by different versions of a given type of module/component(for example, a valve unit 14′) having identical features forconnecting/interfacing with other modules/components. By way of example,a separator system may be potentially use one of several differentversions of valve unit, because these different versions are providedwith common features which allow for mating with the rotor housing 4′even though the valve units may be different in many other respects. Thetable provided by FIG. 36 shows how different components/modules of aseparator system may be optionally provided with a component/module orexchanged for a different version of a component/module.

The present invention is not limited to the specific embodimentsdescribed above. Alternative arrangements and suitable materials will beapparent to a reader skilled in the art.

What is claimed is:
 1. A gas cleaning separator for separating aflowable mixture of substances of difference densities, the separatorcomprising: a housing defining an inner space, a rotor assembly forimparting a rotary motion onto said mixture of substances, the rotorassembly being located in said inner space and rotatable about an axisrelative to the housing, wherein the rotor assembly comprises an inletfor receiving said mixture of substances, an outlet from which saidsubstances are ejected from the rotor assembly during use, and a flowpath for providing fluid communication between the inlet and outlet,wherein the outlet is positioned more radially outward from said axisthan the inlet; and a housing member defining a region for receivingfluid ejected from the rotor assembly and directing said fluid to afirst outlet aperture of the housing; and wherein the housing member isprovided with means for segregating an inlet to said region from fluidwhich, in use, re-circulates back towards said inlet after having flowedpast said inlet.
 2. A separator as claimed in claim 1, wherein saidsegregating means comprises a wall.
 3. A separator as claimed in claim2, wherein said wall extends from a downstream side of said region in adownstream direction with respect to said flow of fluid having, in use,past said region.
 4. A separator as claimed in claim 2, wherein saidwall is spaced from said housing.
 5. A separator as claimed in claim 3,wherein said wall comprises a free end.
 6. A separator as claimed inclaim 5, wherein said free end is spaced from said housing in an axialdirection by an axial distance of between 2 mm and 200 mm.
 7. Aseparator as claimed in claim 6, wherein said free end is spaced fromsaid housing in a direction substantially perpendicular to said axialdirection by a distance less than said axial distance.
 8. A separator asclaimed in claim 2, wherein said wall defines a closed loop.
 9. Aseparator as claimed in claim 2, wherein said wall defines afrusto-conical shape.
 10. A separator as claimed in claim 9, whereinsaid frusto-conical shape has a longitudinal axis coincident with saidaxis of rotation.
 11. A separator as claimed in claim 9, wherein saidfrusto-conical shape diverges in a downstream direction with respect tosaid flow of fluid having, in use, past said region inlet.
 12. Aseparator as claimed in claim 1, wherein the housing member comprisesmeans for supporting the housing member relative to the housing, thesupporting means being located downstream of the segregating means withrespect to said flow of fluid having, in use, past said region inlet.13. A separator as claimed in claim 12, wherein the supporting means isa wall defining a closed loop.
 14. A separator as claimed in claim 13,wherein said wall has a cylindrical shape.
 15. A separator as claimed inclaim 13, wherein said wall has a longitudinal axis coincident with saidaxis of rotation.
 16. A separator as claimed in claim 13, wherein atleast one aperture is provided in said wall at a junction between saidwall and the housing.
 17. A separator as claimed in claim 12, furthercomprising a second outlet aperture of the housing, wherein saidsupporting means is located in a fluid flow path between the secondoutlet aperture and said segregating means.
 18. A separator as claimedin claim 17, wherein the second outlet aperture is arrangedsubstantially concentrically with said axis of rotation.
 19. A separatoras claimed in claim 1, wherein said segregating means is positioned inthe housing such that, in use, fluid flowing past said region inletflows on one side of said segregating means and said fluid whichre-circulates flows on another side of said segregating means.
 20. Aseparator as claimed in claim 1, wherein an outlet passage extendsbetween the housing member and the housing for conveying fluid from saidregion to the exterior of the housing through said outlet aperture, theexterior of said outlet passage being spaced from the housing such thatfluid is free to flow about the entire external perimeter of said outletpassage.
 21. A separator as claimed in claim 20, wherein said outletpassage is separate to the housing member and the housing.